EP0923628B1 - Fuel composition for diesel engines containing oxygenated compounds - Google Patents

Abstract

PCT No. PCT/FR98/01168 Sec. 371 Date May 4, 1999 Sec. 102(e) Date May 4, 1999 PCT Filed Jun. 8, 1998 PCT Pub. No. WO98/56879 PCT Pub. Date Dec. 17, 1998A fuel composition containing, as a major portion, at least one fuel base, and, as a minor portion, at least one oxygenated compound, which contains at least 0.05% by weight of at least one trialkoxyalkane of the formula (I): wherein: X is a divalent hydrocarbon-containing group CnH2n, wherein n is 1, 2, or 3, each hydrogen atom optionally being substituted by a hydrocarbon-containing residue; R1, R'1, and R''1 are each independently linear or branched alkyl groups containing from 1 to 10 carbon atoms and optionally at least one oxygen atom, two of each of R1, R'1 and R''1 groups optionally being connected to form a heterocyclic ring containing 5 or 6 atoms; and R2 is a hydrogen atom or a linear C1-C4 alkyl radical, or R2 and hydrocarbon-containing residue X, together by bonding, form a ring containing 5 or 6 carbon atoms.

Description

The present invention relates to a new fuel composition comprising oxygenated compounds improving fuel combustion, especially compounds that can improve the cetane number of bases fuels such as middle distillates used in the composition of diesel for diesel engines.

It is well known to introduce into the essences of oxygenated components to improve the octane number, such as that MTBE, ETBE and others to replace in particular the lead that was introduced there in the past.

For diesel, we're not talking about an octane number but rather a corresponding cetane number like octane has a fuel combustion characteristic in a combustion engine. This cetane number represents more particularly the ability of the fuel base to ignite in the engine combustion chamber. A cetane number too low corresponds to a self-ignition delay too long which causes late combustion, brutal and incomplete with unburnt formation. This poor combustion results in an increase in exhaust pollutants, an increase in noise corresponding to the auto-ignition of the fuel, especially when the engine is idling, and greater difficulty starting the engine, especially cold, since combustion is delayed. It is therefore preferable for proper engine operation diesel to have a fuel with an index of high cetane. But, this high cetane depends on the nature of the fuel base used and the nature and the effectiveness of additives known as pro-cetane or improving cetane which it is necessary to add to these bases.

A fuel base generally consists of a physical mixture of several middle or cut distillates petroleum products from the refining of crude oils from from all walks of the world. These oil cuts are from a large number of separations by distillation atmospheric or vacuum and chemical transformations of some of these cuts distilled by hydrodesulfurization and or catalytic cracking. By an appropriate mixture of these different refined cuts, we get a wide variety fuel bases with physico-chemical properties relatively different. Finally, diesel fuels or diesel fuels usable in combustion engines are prepared by a complex mixture of these bases. However, to obtain fuels meeting the specifications legal requirements, refiners must develop increasingly complicated formulations which favor crude oils highly concentrated in distillates and fuel bases with a high cetane number.

The small amount of easily refined cuts accessible, with a sufficiently high cetane number, a forced refiners to look for additives or components which, when mixed with these cuts, are likely to increase the cetane number.

Among the additives, i.e. the compounds introduced at low levels in refined cuts, it is known to use nitrates or peroxides organic which are known to have limited effectiveness in fuel bases or diesel fuel with naturally a low cetane number. In addition, organic peroxides are irreversibly broken down into function of time which leads to a degradation of characteristics of diesel stored both in quality and in cetane number.

Refiners have long sought others sources of compounds that can improve the index of cetane from fuel bases and gas oils, in particular among oxygenated compounds such as ethers, polyethers or acetals. Addition of compounds oxygenated in diesel, reduces emissions of pollutants, in particular particle emissions (EP 14 992).

Thus, US patent 5308365 claims the addition of 1 to 30% by weight of dialkylated and trialkylated derivatives of glycerin, obtained by adding an olefin such as isobutene on glycerol, in a diesel having a range of use between 160 ° C and 370 ° C and a sulfur content less than or equal to 500 ppm.

US patent 5,425,790 claims the use of an additive of general formula H- (OA) _n -H or A is of ethylene structure substituted by a methyl or ethyl group and n is an integer between 10 and 25.

Patent JP 0725 8661 claims a formulation comprising 20 to 94% of a diesel cut having a distillation range between 130 ° C and 400 ° C, 5 to 40% of a hydrocracked diesel cut commonly called LCO and 1 to 40 % of a monoether of formula R ₁ OR ₂ in which R ₁ and R ₂ are alkyl chains of 3 to 12 carbon atoms.

Patent JP 0701 8271 claims gas oils containing glycol ethers of formula R ₁ - (OA) _n -R ₂ in which R ₁ is an alkyl chain of 1 to 10 carbon atoms, R ₂ represents the hydrogen atom or an alkyl chain comprising from 1 to 10 carbon atoms, A is of ethylene or trimethylene structure optionally substituted and n is an integer varying from 1 to 10.

Patent JP 0634 0886 claims the addition to a diesel of 0.05% to 20% by weight of a compound of general formula R ₁ -O- (EO) _n - (PO) _m -R ₂ in which R ₁ and R ₂ represent separately the hydrogen atom or an alkyl chain comprising from 1 to 20 carbon atoms, EO and PO respectively representing the oxyethylene and oxyisopropylene groups, and, m and n are whole numbers between 0 and 15.

On the other hand, patent FR 2,544,738 claims, as a component of diesel fuels, acetals of formula C ₄ H ₉ -O-CR ₁ R ₂ -OC ₄ H ₉ , R ₁ and R _{2 which} may be hydrogen or one, alkyl group.

However, these prior art compounds, in especially low molecular weight acetals or again ethers containing several oxygen atoms, have a major drawback related to their character high hydrophilic favoring the trapping of water in the fuels. However, it is well known that water in fuels generates corrosion and wear of mechanical parts, and moreover, that it promotes development of bacteria in the circuit that clog filters and power systems, which results in a engine malfunction.

Another disadvantage of these oxygenated compounds particular ethers and polyethers is related to their mode multi-stage manufacturing which makes them expensive and limits their continuous production on a large scale.

The present invention relates to the use of a new family of oxygenated compounds in fuels Diesel, which increase the cetane number, provide greater flexibility in the formulation of Diesel fuels for a lower cost and allow in besides limiting aromatic and sulfur compounds responsible for the emission of particles.

   dans laquelle ;

• X correspond à un groupement hydrocarboné divalent C_nH_2n dont n est égal à 1, 2 ou 3, chaque atome d'hydrogène étant éventuellement substitué par un reste hydrocarboné,
• R₁, R'₁ et R"₁ sont des groupements alkyls linéaires ou ramifiés, identiques ou différents comprenant de 1 à 10 atomes de carbone et éventuellement au moins un atome d'oxygène, deux des groupements R₁, R'₁ et R''₁ étant éventuellement reliés pour former un hétérocycle de 5 à 6 atomes;
• et R₂ étant un atome d'hydrogène ou un radical alkyl linéaire comprenant de 1 à 4 atomes de carbone, R₂ pouvant même former par liaison avec un reste hydrocarboné de X un cycle comprenant de 5 à 6 atomes de carbone.

The subject of the present invention is therefore a fuel composition comprising a major part of at least one fuel base and a minor part of at least one oxygenated compound characterized in that it contains at least 0.05% by weight of at least one trialkoxyalkane of general formula (I) below:

in which ;

• X corresponds to a divalent hydrocarbon group C _n H _{2n of} which n is equal to 1, 2 or 3, each hydrogen atom being optionally substituted by a hydrocarbon residue,
• R ₁ , R ' ₁ and R " ₁ are identical or different linear or branched alkyl groups comprising from 1 to 10 carbon atoms and optionally at least one oxygen atom, two of the groups R ₁ , R' ₁ and R '' ₁ being optionally linked to form a heterocycle of 5 to 6 atoms;
• and R ₂ being a hydrogen atom or a linear alkyl radical comprising from 1 to 4 carbon atoms, R ₂ may even form, by bond with a hydrocarbon residue of X, a ring comprising from 5 to 6 carbon atoms.

In the context of the present invention, this fuel composition contains 60 to 99.95% by weight at least one fuel base and from 0.05 to 40% by weight of trialkoxyalkane of formula (I).

By fuel base is meant any petroleum cut after refining, either by distillation or by treatment of these distilled cups.

dans laquelle ;

• R₁, R'₁ et R''₁ sont des groupements alkyls linéaires ou ramifiés, identiques ou différents comprenant de 1 à 10 atomes de carbone et éventuellement au moins un atome d'oxygène, deux des groupements R₁, R'₁ et R''₁ étant éventuellement reliés pour former un hétérocycle de 5 à 6 atomes;
• R₂, R₃, R₄ et R'₄ sont des groupements identiques ou différents représentant l'hydrogène ou un radical alkyl linéaire comprenant de 1 à 4 atomes de carbone, R₂ pouvant même former par liaison avec R₄ ou R'₄ un cycle comprenant de 5 à 6 atomes de carbone.

In a first embodiment of the invention, the trialkoxyalkane is chosen from the trialkoxypropanes of formula (II) below:

in which ;

• R ₁ , R ' ₁ and R'' ₁ are identical or different linear or branched alkyl groups comprising from 1 to 10 carbon atoms and optionally at least one oxygen atom, two of the groups R ₁ , R' ₁ and R '' ₁ being optionally linked to form a heterocycle of 5 to 6 atoms;
• R ₂ , R ₃ , R ₄ and R ' ₄ are identical or different groups representing hydrogen or a linear alkyl radical comprising from 1 to 4 carbon atoms, R ₂ can even form by bond with R ₄ or R' ₄ a cycle comprising from 5 to 6 carbon atoms.

In a first embodiment of the invention, in formula (II), R ₂ , R ₃ , R ₄ and R ' ₄ are the hydrogen atom.

In a first variant of this first mode, R ₁ , R ' ₁ and R'' ₁ are identical and are chosen from alkyl groups comprising from 1 to 4 carbon atoms.

The trialkoxyalkane compounds thus obtained from the invention are chosen from the group consisting of trimethoxypropane, triethoxypropane, tripropoxypropane, tributoxypropane.

In a second variant of this first mode, R ₁ , R ' ₁ and R'' ₁ comprise from 1 to 4 carbons and at least one oxygen atom.

Among the compounds thus constituted, it will be chosen to preferably in the group made up of the tri (methoxyethoxy) propane and tri (ethoxyethoxy) propane.

In a third variant of this first mode, R ₁ is an alkyl group comprising from 1 to 4 carbon atoms and R ' ₁ and R'' ₁ are linked and constitute a chain of 2 to 3 carbons so as to form with the two oxygen atoms a heterocycle of 5 to 6 atoms. Among these compounds, 2- (2-hydroxyethyl) ethoxy-1,3-dioxolane is preferred.

In a second embodiment of the invention, in formula (II), R ₄ is an alkyl group of 1 to 4 carbon atoms, R ₂ , R ₃ and R ' ₄ are hydrogen atoms and R ₁ , R ' ₁ and R''1 are alkyl groups comprising from 1 to 5 carbon atoms.

Among the compounds thus defined, the 1,1,3-trimethoxybutane, 1,1,3-triethoxybutane, 1,1,3-tripropoxybutane and 1,1,3-tributoxybutane.

In a third preferred embodiment of the invention, in formula (II) R ₂ or R ₃ is an alkyl group comprising 1 to 4 carbon atoms, R ₄ , R ' ₄ and, R ₂ or R ₃ , are atoms of hydrogen, and R ₁ , R ' ₁ and R'' ₁ are alkyl groups comprising from 1 to 5 carbon atoms.

Among the preferred compounds of this variant, the 1,1,3-triethoxy-2-methylpropane and 1,3,3-triethoxybutane are preferred.

In a fourth embodiment of the invention, in formula (II), R ₃ and R ₄ are hydrogen atoms, R ₂ and R ' ₄ are linked to form a saturated ring comprising from 5 to 6 atoms carbon, R ₁ , R ' ₁ and R'' ₁ are alkyl groups comprising from 1 to 5 carbon atoms.

Among the compounds constituting this variant of the invention, 1,1,3-triethoxycyclohexane is preferred.

To implement the invention, the basics fuels are chosen from refined cuts distilling between 170 and 370 ° C containing at most 50% by weight aromatics, and less than 0.2% by weight of compounds sulfur.

The examples below are given as illustrative but not limiting of the invention.

EXAMPLE I Preparation of 1,1,3-triethoxypropane

The synthesis of 1,1,3-triethoxypropane was carried out according to a patent FR 1,447,138 of January 30, 1964. The catalyst used for the reaction is a resin acid sulfonic. The final neutralization, which was not mentioned in this patent, is made with a resin basic.

800g of absolute ethanol (17.4 mol) and 25g of Amberlyst® 15 resin (Aldrich), previously washed with ethanol and dried, are charged to a 2L reactor. At 50 ° C., 185 g of acrolein (3.3 mol) are introduced over a period of 4 hours. At the end of the addition, the mixture is left to react for 3 hours at 50 ° C. The reaction mixture is filtered, neutralized with stirring for one hour with 8 g of Amberlyst® A21 resin (Aldrich, previously washed with ethanol), then filtered again. After distillation (T _eb = 75-78 ° C / 2500 Pa, ie 25 mbar), 390 g of 1,1,3-triethoxypropane are obtained (Yield = 67%).

EXAMPLE 2

L'indice du cétane IC du 1,1,3-triéthoxypropane pur est déduit de la valeur mesurée du cétane du mélange, en supposant une loi de mélange linéaire, selon l'équation : IC (1,1,3-triéthoxypropane) = IC mélange - 0,8 IC gazole0,2 MELANGE COMPOSITION IC
Mélange 1,1,3-triéthoxypropane A 80% gazole A
20% 1,1,3-triéthoxypropane 55,6 78 B 80% gazole B
20% 1,1,3-triéthoxypropane 59,8 83 The cetane number of 1,1,3-triethoxypropane prepared according to example 1 was measured according to standard ASTM D613, in a 20% mixture in two gas oils whose characteristics are indicated below:

The cetane index IC of pure 1,1,3-triethoxypropane is deduced from the measured value of cetane of the mixture, assuming a linear mixing law, according to the equation: IC (1,1,3-triethoxypropane) = IC mixture - 0.8 IC diesel 0.2 MIXED COMPOSITION IC
Mixed 1,1,3-triethoxypropane AT 80% diesel A
20% 1,1,3-triethoxypropane 55.6 78 B 80% diesel B
20% 1,1,3-triethoxypropane 59.8 83

EXAMPLE 3

In this example, we compared the cetane number, boiling temperature and water solubility of triethoxy-1,1,3 propane and those of components already known or cited in the prior art.

A compound having a cetane number higher than 70, and a boiling point of at least 160 ° C and a very low solubility in water can be considered as an ideal component usable in a diesel. Compound Temperature
boiling point (° C) Solubility in
the water (%) Index of
cetane 1,1,3 tri-ethoxypropane 180 <1 80 Ethylene ether glycol 135 miscible 38 Ethyl, ethylene glycol butyl ether 140 # 4 51 Diethylene glycol ethyl ether 202 miscible 54 Diethylene glycol butyl ether 230 miscible 59 Methyl, diethylene glycol butyl ether 196 # 10 55 Diethylene glycol dimethyl ether 162 miscible 61 Diethylene glycol diethyl ether 177 miscible 95 Formaldehyde diethylacetal 89 miscible 57 Formaldehyde dibutylacetal 177 <5 65

Claims (15)

1. Fuel composition comprising 60 to 99.95% by weight of at least one fuel base and from 0.05 to 40% by weight of trialkoxyalcane of general formula (I) below:

   

      in which:

   X corresponds to a divalent hydrocarbon-comprising group C_nH_2n in which n is equal to 1, 2 or 3, each hydrogen atom optionally being substituted by a hydrocarbon-comprising residue;

   R₁, R'₁ and R"₁ are identical or different, linear or branched, alkyl groups comprising from 1 to 10 carbon atoms and optionally at least one oxygen atom, two of the R₁, R'₁ and R"₁ groups optionally being connected in order to form a heterocycle comprising 5 to 6 atoms;

   and R₂ being a hydrogen atom or a linear alkyl radical comprising from 1 to 4 carbon atoms, it even being possible for R₂ to form, by bonding with a hydrocarbon-comprising residue of X, a ring comprising from 5 to 6 carbon atoms.
2. Fuel composition according to Claim 1, characterized in that the trialkoxyalcane is chosen from trialkoxypropanes of formula (II) below:

   

   in which:

   R₁, R'₁ and R"₁ are identical or different, linear or branched, alkyl groups comprising from 1 to 10 carbon atoms and optionally at least one oxygen atom, two of the R₁, R'₁ and R"₁ groups optionally being connected in order to form a heterocycle comprising 5 to 6 atoms;

   R₂, R₃, R₄ and R'₄ are identical or different groups representing hydrogen or a linear alkyl radical comprising from 1 to 4 carbon atoms, it even being possible for R₂ to form, by bonding with R₄ or R'₄, a ring comprising from 5 to 6 carbon atoms.
3. Fuel composition according to Claim 2, characterized in that R₂, R₃, R₄ and R'₄ in the formula (II) correspond to a hydrogen atom.
4. Fuel composition according to either of Claims 2 and 3, characterized in that R₁, R'₁ and R"₁ are identical and are chosen from alkyl groups comprising from 1 to 4 carbon atoms.
5. Fuel composition according to Claims 2 to 4, characterized in that the compounds of formula (II) are chosen from the group consisting of trimethoxypropane, triethoxypropane, tripropoxypropane and tributoxypropane.
6. Fuel composition according to Claims 2 and 3, characterized in that R₁, R'₁ and R"₁ comprise from 1 to 4 carbons and at least one oxygen atom.
7. Fuel composition according to Claims 2, 3 and 6, characterized in that the compounds of formula (II) are chosen from the group consisting of tri(methoxyethoxy)propane and tri(ethoxyethoxy)propane.
8. Fuel composition according to Claims 2 and 3, characterized in that R₁ is an alkyl group comprising from 1 to 4 carbon atoms and R'₁ and R"₁ are connected and constitute a linkage comprising 2 to 3 carbons, so as to form, with the two oxygen atoms, a heterocycle comprising 5 to 6 atoms.
9. Fuel composition according to Claims 2, 3 and 8, characterized in that the compound of formula (II) is 2-(2-hydroxyethyl)ethoxy-1,3-dioxolane.
10. Fuel composition according to Claim 2, characterized in that, in the formula (II), R₄ is an alkyl group comprising from 1 to 4 carbon atoms, R₂, R₃ and R'₄ are hydrogen atoms and R₁, R'₁ and R"₁ are alkyl groups comprising from 1 to 5 carbon atoms.
11. Fuel composition according to Claims 2 and 10, characterized in that the compounds of formula (II) are chosen from the group consisting of 1,1,3-trimethoxybutane, 1,1,3-triethoxybutane, 1,1,3-tripropoxybutane and 1,1,3-tributoxybutane.
12. Fuel composition according to Claim 2, characterized in that, in the formula (II), R₂ or R₃ is an alkyl group comprising 1 to 4 carbon atoms, R₄, R'₄ and R₃ (or R₂) are hydrogen atoms and R₁, R'₁ and R"₁ are alkyl groups comprising from 1 to 5 carbon atoms.
13. Fuel composition according to Claims 2 and 12, characterized in that the compounds of formula (II) are chosen from the group consisting of 1,1,3-triethoxy-2-methylpropane and 1,3,3-triethoxybutane.
14. Fuel composition according to Claim 2, characterized in that, in the formula (II), R₃ and R₄ are hydrogen atoms, R₂ and R'₄ are connected in order to form a saturated ring comprising from 5 to 6 carbon atoms and R₁, R'₁ and R"₁ are alkyl groups comprising from 1 to 5 carbon atoms.
15. Fuel composition according to Claims 2 and 14, characterized in that the compound of formula (II) is 1,1,3-triethoxycyclohexane.