FR2492402A1 - Diesel fuels contg. fatty acid ester(s) - obtd. e.g. by methanolysis of vegetable or animal fats or oils - Google Patents

Abstract

A compsn. useful as a diesel fuel comprises (a) 0-90 (pref. 0-70) vol% of a gas oil and (b) one or more fatty acid esters R1COOR2, where R1 is C5-C23 (pref. C11-C23) aliphatic, substantially linear, satd. or unsatd.; and R2 is C1-C12 aliphatic, linear or branched, satd. or unsatd. The ester may be the mixt. obtd. from alcoholysis of a vegetable or animal fatty material, pref. with methanol. The compsn. has cetane index of at least 40, pref. at least 50. Components (b) derived from fatty material have higher cetane indices than the fats themselves and have better low temp. properties, viscosity and boiling range for fuel use. The esters (e.g. Me esters) are of non-petroleum origin.

Description

 Combustible compositions containing esters of fatty acids, suitable for use as diesel fuels.

 The invention relates to novel fuel compositions, particularly fuels for diesel engines which contain a significant proportion of certain fatty acid esters. According to the invention, the fuel (or fuel) may consist essentially of one or more fatty acid esters or a mixture of such esters with a conventional gas oil, to which may be added conventional additives.

 Fats (oils and fats) of vegetable and animal origin have often been proposed as alternative fuels for diesel engines. It has been advocated as well mixtures of these products with gas oils, that to use them as such. Their cetane number, which reflects the tendency to self-ignition is generally acceptable, although lower than that of gas oils.

 However, certain physicochemical characteristics of these fats are very different from those required of a fuel of the diesel type, in particular from the point of view of the carbon condensation of the molecules, the viscosity and the distillation domain. products considered. For example, one of the constituents most frequently found in fats of vegetable or animal origin, glycerol tris-oleate contains 57 carbon atoms, whereas the hydrocarbon constituents of a gas oil generally contain from 9 to 18 carbon atoms. carbon atoms. In addition, the oils and fats are much more viscous than diesel and do not distil, like the average petroleum fractions, at atmospheric pressure. These particularities constitute a definite obstacle to the use of fats of vegetable origin or as diesel fuels (or as constituents of diesel fuels).

 It has now been discovered that it is possible to obtain, from fats, in particular oils and fats of vegetable and animal origin, products having characteristics much better adapted for use as fuels in diesel engines.

In general, the fuel compositions of the invention can be defined as comprising
a proportion of 0 to 90% by volume of at least one conventional diesel fuel; and
a proportion of 100 to 10% by volume of at least one fatty acid ester corresponding to the general formula R1-C00-R2 in which R represents a substantially linear aliphatic radical, saturated or unsaturated, containing from 5 to 23 atoms of carbon and R2 represents a linear or branched, saturated or unsaturated aliphatic radical containing from 1 to 12 carbon atoms.

The compositions of this type which can be used according to the invention as diesel engine fuels are those which have a cetane number satisfying the specifications (for the United States, the cetane number must be at least 40, it is in general 40 to 47, for France, it must be at least 50, it is generally 50 to 55)
The cetane number for fuels is determined according to ASM D 613-65.

Preferably, the "fatty acid" part of the esters used in the invention is derived from R COOR acids in which the linear, saturated or unsaturated aliphatic radical R1 contains from 11 to 23 carbon atoms; it derives more particularly
saturated fatty acids, such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, or lignoceric acid.

 fatty acids with ethylenic unsaturation, such as lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid or erucic acid.

 or else fatty acids with 2 or more ethylenic unsaturations such as linoleic acid or linolenic acid.

 The "fatty acid" part of the esters used in the invention may further derive from mixtures of fatty acids containing predominant proportions of some of the acids mentioned above and originating in particular from natural fats of vegetable or animal origin.

Among the fatty substances of plant origin, mention may be made of rapeseed oils, for example those whose fatty acid composition shows predominant proportions of erucic acid (about 50%), linoleic acid (approx. 14%), oleic acid (about 13% and gadoleic acid (about 10%), and those containing only small proportions of erucic acid;
or sunflower oil whose fatty acid composition shows predominant proportions of linoleic acid (about 60%), and oleic acid (about 26%).

 Other examples include coconut oil, corn oil, cottonseed oil, soybean oil or peanut oil.

 Among the fatty substances of animal origin, mention may be made, for example, of lard, whose fatty acid composition reveals predominant proportions of oleic acid (about 42%), palmitic acid (approx.

27%) and stearic acid (about 19 yO);
or beef tallow, whose fatty acid composition shows predominant proportions of oleic acid (about 36%), palmitic acid (about 26% and stearic acid (about 23%).

 The "alcohol" part of the esters used in the invention is derived from saturated or unsaturated aliphatic monoalcohols, linear or branched, having from 1 to 12 carbon atoms. For the sake of convenience, it is most often derived from methanol. But it can still derive for example from methanol, n-propanol, isopropanol, n-butanol, isobutanol, etc. or else ethyl 2-hexanol or dodecanol.

 The fatty acid esters considered in the invention can advantageously be obtained by alcoholysis (or transesterification) using a R monoH monohydric alcohol, glycerol esters contained in natural fats (oils or fats) of plant or animal origin. .

This alcoholysis can be carried out advantageously on the oils and fats in the raw state, that is to say without it being necessary to separate them into their various glyceride constituents.

 For example, the preparation of methyl esters derived from triglycerides is carried out by methanol alcoholysis under conditions conriiesen the art (described for example in US Patent 2360844).

 The fatty acid esters used in the invention may still - although less desirable - be synthesized from the fatty acids themselves when readily available.

In this case, one operates by simple esterification of the fatty acid
R1 COOR by means of the appropriate aliphatic monohydric alcohol R20R, according to any usual technique.

 The fatty acid esters considered in the invention, as defined above, may be used alone or in mixtures with one another as essential constituents of the fuel compositions (especially for diesel engines) according to the invention.

 They can also be used in mixture with conventional gas oils, in various proportions. The advantages of using the fatty acid esters are chiefly apparent in this case when at least 0.0, by volume of fatty ester of fatty ester is used for 70% of gas oil.

 By conventional gas oils is meant in the invention, cuts of petroleum origin boiling in a range from 1200-1900C to 300 -380 C, having an average molecular weight of about 200 (the molecular weight of the constituents of gas oils can go from about 130 to about 250). They also have a variable content of aromatic hydrocarbons (for example from 20 to 35% by weight). Their kinematic viscosity at 20 ° C is generally a few centistokes, for example about 4 to 9 cSt. They have a cetane number of about 38 to 58.

 These gas oils can come from the atmospheric distillation of crude oil or other refining operations such as cracking or hydrocracking.

Unlike synthetic fuels or non-oil fuels (coal, biomass), which are generally poorly suited for use in diesel engines, the products considered in the invention generally have very good cetane numbers, and when mixed with gas oils, they exhibit particularly high "mixing indices",
("The Cetane Mix Index" of a product is the calculated cetane number that the product should present so that, knowing the cetane number of the gas oil used, the weighted average - by the proportions of diesel and product - between the cetane number of the gas oil and the "melt index" of the product is equal to the cetane number measured for the mixture) 0
Another advantage of the fatty acid esters used in the invention is that their preparation can be carried out without the use of any product of petroleum origin, the alcohols (methanol, ethanol, etc.) being able to same beech obtained from biomass.

 The availability of raw materials is varied and multiple: rapeseed oil in France and in various other Western countries, animal fats (tallow, lard, etc.), tropical crops.

 The esters of fatty acids considered in the invention, as defined above, may exhibit ethylenic unsaturation more or less important depending on the nature of the products used in their preparation.

 In certain cases, it is possible, without departing from the scope of the invention, to subject the fatty acid esters to a selective hydrogenation intended to reduce the unsaturation thereof. This selective hydrogenation can be carried out using any suitable technique.

 This treatment has the effect of raising the cetane number of the product, which can be advantageous, especially when the fatty acid ester (or the mixture of fatty acid esters) is used in mixture with gas oils with a high aromatic content, which generally have slightly low cetane numbers.

 However, it is not always beneficial to lower the degree of unsaturation of the fatty acid esters contemplated in the invention since, as it approaches the complete saturation of the ethylenic double bonds, there is a risk of deteriorating the low temperature behavior of fatty acid esters, and in particular to cause their cold precipitation in gas oils.

 In their use as fuels for diesel engines, can be added to the compositions of the invention various customary additives compatible with the fatty acid esters involved. Thus, it may be recommended to incorporate antioxidant additives. They can also be added additives-improving cold characteristics, anti-smoke additives, etc.

 The following examples illustrate the invention and should in no way be considered as limiting.

 First of all, the preparation of the methyl esters of rapeseed oil, lard and tallow, which will be used among others in the examples illustrating the invention.

PREPARATION A
Preparation of the methyl esters of rapeseed oil.

In a 10-liter glass Grignard reactor equipped with an agitator, thermometer, bottom-bottom valve and outer chanter, 5 kg of refined rapeseed oil are introduced beforehand. dehydrated for 2 hours at 1000C under a pressure of 6.5 to 7 millibars
The main characteristics of the rapeseed oil thus treated are shown in Table 1 which will be found later. It also has a saponification number of 192 (mg KOH / g).

 With stirring turned on, the oil is heated to 55-600 ° C whereupon a solution consisting of 876 g of absolute methanol and 9 g of sodium metal is incorporated in the course of 5 minutes. Allowed to react for 1 hour then stop stirring.

 After 30 minutes of decantation, the bottom phase consisting essentially of glycerol (650 g) is removed by the bottom valve. 520 cm3 of distilled water previously heated to 600 ° C. are then added to the organic phase contained in the reactor. After vigorous stirring for 15 minutes, the mixture is allowed to stand for the same time. The aqueous decanted washing phase is removed as before. The washing operation is repeated twice with 320 cm 3 of water.

 The recovered organic phase is dried over anhydrous sodium sulphate, filtered briefly and then evaporated at 1000C under reduced pressure (6.5 to 7 millibars) for 1 hour, in order to remove the last traces of methanol.

 Finally, 4750 g of the desired product are obtained, the analysis of which reveals a methyl ester content greater than 95% by weight. The main characteristics of these esters are also given in Table 1.

PREPARATION 3
Preparation of methyl esters of lard.

 Under the same operating conditions as those described above (preparation A), the alcoholysis of 6 kg of commercial lard, previously dehydrated at 1000C under a pressure of 6.5 to 7 millibars, is carried out for 2 hours.

The lard thus treated has the following characteristics
Acid number 1.3 (mg KOH / g)
Saponification index 199 (mg KOE / g)
The alcoholysis is carried out with 1090 g of absolute methanol and 14 g of sodium.

 Analysis of the organic phase obtained (6241 g) reveals a methyl ester content of about 97% by weight. The main characteristics of these esters are given in Table 2.

PREPARATION C
Preparation of methyl esters of tallow

 As previously described (preparation A), the alcoholysis of 6 kg of industrial tallow, previously dehydrated under the conditions already mentioned, is carried out.

The characteristics of the tallow thus treated are
Acid number 2.25 (mg KOH / g)
Saponification index 196 (mg KOH / g)
The alcoholysis is carried out using 1073 g of anhydrous methanol and 15 g of sodium metal.

 Analysis of the organic phase obtained (6190 g) reveals a methyl ester content of about 97% by weight. The main characteristics of these esters are given in Table 2 below.

 Table 1 below gives a comparison between various characteristics of the rapeseed oil and the corresponding characteristics of the mixture of methyl esters derived therefrom by alcoholysis with methanol, carried out for example according to Preparation A described above.

 The corresponding properties of methyl oleate have also been reported.

TABLE 1

<tb><SEP> 1 <SEP> I
<tb><SEP> Product <SEP> Ruile <SEP> of <SEP> colsa <SEP> Esters <SEP> Methyl <SEP> Oleate <SEP> of
<tb> Characteristics <SEP> of <SEP> oil <SEP> of <SEP> rapeseed <SEP> methyl
<tb><SEP> colsa <SEP> methyl
<tb> Density <SEP> (200C) <SEP> 0.916 <SEP> 0.880 <SEP> 0.877
<tb> Point <SEP> flash <SEP> 285 <SEP> - <SEP> 188 <SEP> 182
<tb> (vase <SEP> closed) <SEP> (Oc)
<tb><SEP> acid number <SEP> 0.05 <SEP> 0.05 <SEP> 0.75
<tb> (mg <SEP> R / g)
<tb> Viscosity
<tb> (cSt) <SEP> to <SEP> 200G <SEP> 77.8 <SEP> 7.52 <SEP> 7.30
<tb><SEP> to <SEP> 500C <SEP> 25.7 <SEP> 3.75 <SEP> 3.70
<tb> Point <SEP> of <SEP> disorder <SEP> (OC) <SEP> - <SEP> 11 <SEP> - <SEP> 3 <SEP> - <SEP> 10
<tb> Flow Pt <SEP><SEP> (OC) <SEP> - <SEP> 21 <SEP> -12 <SEP> - <SEP> 15
<tb> eLF <SEP> (OC) <SEP> + <SEP> 20 <SEP> -12 <SEP> - <SEP> 12
<tb><SEP> Index of <SEP> cetane <SEP> 28 <SEP> 45 <SEP> 52
<tb> Distillation
<tb> Point <SEP> Initial <SEP> (OC) <SEP> 160 <SEP> 321 <SEP> 303
<tb> 10 <SEP>% <SEP> (oc3 <SEP> 256 <SE> 336 <SEP> - <SEP> 320
<tb><SEP> (cracking)
<tb> Point <SEP> Final <SEP> (OG) <SEP> - <SEP> 350 <SEP> 346
<tb><SEP> (cracking)
<Tb>
These indications make it possible to demonstrate the advantages that the methyl esters of rapeseed oil have over the rapeseed oil itself, mainly from the point of view of the cetane number, the density, the viscosity, the filterability limit temperature, as well as the distillation range.

 The properties of the methyl esters of rapeseed oil and methyl oleate are, unexpectedly, quite satisfactory for their use in diesel fuels.

 Table 2 below shows the characteristics of the methyl esters of lard and tallow, prepared as described above (preparations B and C, respectively).

TABLE 2

<tb><SEP> Products <SEP> Esters <SEP> Methylics <SEP> Esters <SEP> Methyl
<tb><SEP><SEP><SEP><SEP> Lard <SEP> Characteristics of Tallow
<tb><SEP> 0.870 <SEP> 0.872
<tb> Density <SEP> (at <SEP> 200C) <SEP> 0.870 <SEQ> 0.872
<tb> Point <SEP> Flash <SEP> (OC) <SEP> 180 <SEP> 181
<tb><SEP> (vase <SEP> closed)
<tb><SEP> acid number <SEP> 0.01 <SEP> 0.05
<tb><SEP> (mg <SEP> HOH / g)
<tb> Viscosity <SEP> (at <SEP> 50 C) (cSt) <SEP> 4.05 <SEP> 3.90
<tb><SEP>Index><SEP> Cetane <SEP> 56 <SEP> 58
<tb> Distillation
<tb> Point <SEP> Initial <SEP> (OG) <SEP> 309 <SEP> 302
<tb> Point <SEP> Final <SEP> (OG) <SEP> 340 <SEP> 340
<Tb>
From these results it is found that the methyl esters of lard and tallow are, surprisingly, quite suitable for use in diesel fuels.

 In Table 3 presented below, the cetane number of fuel compositions consisting of esters of fatty acids used alone or in a mixture in various proportions with two different gas oils has been indicated, one having a cetane number of 54, the other 45.

 The fatty acid esters considered were the methyl esters of rapeseed oil, methyl oleate (from two different lots); methyl esters of lard; methyl esters of tallow; methyl stearate; and 2-ethylhexyl stearate.

 For mixtures with gas oils, the "cetane number of mixture" (calculated) of the fatty acid ester in question was also indicated.

 By way of comparison, the value of the cetane number of the rapeseed oil was recalled and the cetane number of mixtures at 50% by volume with cetane number 54 diesel fuel of saindoum and tallow respectively.

TABLE 3

<tb><SEP> GAS <SEP> I <SEP> (IC = 54) <SEP> GAS <SEP> II <SEP> (10 = 45) <SEP>
<tb><SEP> Compositions <SEP> ï <SEP><SEP> Index of <SEP><SEP><SEP> Index <SEP><SEP> Index <SEP> Index
<tb><SEP> cetane <SEP> cetane
<tb><SEP> measured <SEP> mixture <SEP> measured <SEP> mixture
<tb> (*) <SEP> Oil <SEP> of <SEP> rapeseed
<tb><SEP> 100 <SEP>% <SEP> flight <SEP> 28 <SEP> - <SEP> 28 <SEP>
<tb> Esters <SEP> Methyl
<tb> of <SEP> rapeseed
<tb><SEP> 100 <SEP>% <SEP> flight <SEP> 45
<tb><SEP> 90 <SEP>% <SEP>"<SEP> 48 <SEP>47'3<SEP>
<tb><SEP> 75 <SEP>% <SEP>"<SEP> 49 <SEP> 47.3
<tb><SEP> 50 <SEP>% <SEP>"<SEP> 51 <SEP> 48
<tb> Oleate <SEP> of <SEP> Methyl
<tb><SEP> 100 <SEP>% <SEP> vol <SEP> 52 <SEP> (the <SEP> batch) <SEP> 50.5 <SEP> (2nd <SEP> batch)
<tb><SEP> 90 <SEP> 5% <SEP>"<SEP> 53 <SEP> 52.9 <SEP> 54.5 <SE> 55.6
<tb><SEP> 75 <SEP>% <SEP>"<SEP> 58 <SEP> 59.3 <SEP> 50.4 <SE> 52.2
<tb><SEP> 50 <SEP>% <SEP>"<SEP> 56 <SEP> 58 <SEP> 49.9 <SEP> 54.8
<tb> (*) <SEP> Lard
<tb><SEP> 50 <SEP>% <SEP> flight <SEP> 50.4 <SEP> 46.8
<tb> Esters <SEP> Methyl
<tb> of <SEP> lard
<tb><SEP> 100 <SEP>% <SEP> flight <SEP> 56 <SEP> - <SEP> 56 <SEP>
<tb><SEP> 75 <SEP>% <SEP>"<SEP> 57.5 <SEP> 58.7 <SEP> 56.7 <SEP> 60.6
<tb><SEP> 50 <SEP>% <SEP>"<SEP> 57 <SEP> 60 <SEP> 52.5 <SEP> 60
<tb> (*) <SEP> Tallow
<tb><SEP> 50 <SEP>% <SEP> flight <SEP> 49.9 <SEP> 45.8
<tb> Esters <SEP> Methyl
<tb> to <SEP> tallow <SEP> 75 <SEP>% <SEP> flight <SEP> 60 <SEP> 62
<tb> Esters <SEP> Methyl
<tb> of <SEP> tallow <SEP> 75 <SEP>% <SEP> flight <SEP> 60 <SEP> 62
<tb><SEP> 50 <SEP>% <SEP>"<SEP> 58 <SEP> 62
<tb> Stearate <SEP> of <SEP> Methyl
<tb><SEP> 50 <SEP>% <SEP> flight <SEP> 66.5 <SEP> 79
<tb> Stearate <SEP> of ethyl
<tb> 2 <SEP> hexyl <SEP> 50 <SEP>% <SEP> vol <SEP> 61.7 <SEP> 69.4
<tb> (*) These tests are given for comparison.

 As can be seen, the compositions according to the invention exhibit cetane numbers (and, where appropriate, "cetane mixture indices") quite satisfactory, unlike fatty substances, used alone (rapeseed oil) or even when mixed with a diesel fuel (lard and tallow).

TESTING ON DIESEL ENGINE
Some of the compositions of the invention have been tested on an agricultural tractor diesel engine (rotating at 2400 rpm) for 50 hours each.

It was - pure methyl oleate (2nd batch); - a blend of 75% - 25% methyl oleate in an American diesel
cetane number 45; - pure methyl esters of lard; - a mixture of 75% - 25% methyl esters of lard in
ketone index 45 - 50% - 50% methyl esters of tallow in a diesel fuel
cetane number 54. (The percentages are by volume).

 These tests did not lead to any operating incidents. No deposits were observed at the level of the injectors. Furthermore, a normal maintenance of the energy efficiency of the engine was observed.

Claims (15)

REVEEDICAUIONS 1- combustible composition characterized in that it comprises  from 0 to 90% by volume of at least one diesel and  from 100 to 10 gb by volume of at least one fatty acid ester having the general formula R -COO-R wherein R1 represents a substantially linear, saturated or unsaturated aliphatic radical containing from 5 to 23 carbon atoms and R represents an aliphatic radical, saturated or unsaturated, linear or branched, containing from 1 to 12 carbon atoms. 2- Composition according to claim 1, characterized in that it has a cetane number of at least 40. 3. Composition according to claim 1, characterized in that it has a cetane number of at least 50. 4- Composition according to one of claims 1 and 3, characterized in that the acid portion RI-CO of the ester of formula R1-000-R derives mainly from at least one acid R1 -COOR whose radical R contains from 11 to 23 carbon atoms. 5- Composition according to claim 4, characterized in that the acid R1-COOH is selected from lauric acid, lauroleic acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, gadoleic acid, behenic acid, erucic acid and lignoceric acid. 6. Composition according to one of claims 1 to 5, characterized in that the alcohol portion OR2 of the ester of formula R1-COO-R2 is derived from at least one saturated aliphatic monoalcohol of 1 to 12 carbon atoms. 7- Composition according to claim 6, characterized in that said monoalcohol is methanol. 8- Composition according to one of claims 1 to 7, characterized in that R1 -COO-R represents a mixture of esters resulting from alcoholysis, using a suitable aliphatic monoalcohol, a fatty substance of plant or animal origin. 9- Composition according to claim 8, characterized in that the fatty substance of vegetable origin is selected from coconut oil, rapeseed oil, sunflower oil, corn oil, cottonseed oil , soybean oil and peanut oil. 10. Composition according to claim 8, characterized in that the fatty substance of animal origin is chosen from lard and tallow. 11. Composition according to one of claims 1 to 10, characterized in that said fatty acid ester has undergone a selective hydrogenation treatment. 12. Composition according to one of claims 1 to 11, characterized in that said gas oil consists of a cut of petroleum origin whose distillation range is from 1200C-1900C to 3000-3800C and which has a cetane number from about 38 to 58.  . from 100 to 30% by volume of fatty acid ester.  . from 0 to 70% by volume of diesel and 13.- Composition according to one of claims 1 to 12, characterized in that it comprises 14.- composition according to one of claims 1 to 13, characterized in that it further contains an appropriate proportion of at least one antioxidant additive. 15.- Use of a composition according to one of claims 1 to 14 for supplying a diesel engine.