BRPI0619727B1 - unleaded aviation fuel - Google Patents

Abstract

unleaded aviation fuel. unleaded aviation fuel composition of a mon size greater than 100 made of a larger avgas fuel component and a minor component of at least two ester group compounds of at least one mono or polycarboxylic acid and at least one mono or polyol, anhydrides of at least one mono or polycarboxylic acid, preferably aromatic ethers at a level of at least 5% by weight and ketones at a level of more than 10% by weight.

Description

LEAD-FREE AVIATION FUEL

FIELD OF THE INVENTION The present invention relates to a lead-free avgas (Avgas) fuel composition designed for piston engine or reciprocating aircraft. In particular, a subject of the present invention is a high octane unleaded aviation fuel with very good combustion characteristics.

TECHNOLOGICAL BACKGROUND

Aviation Fuel is a product that has been carefully developed and subjected to strict standards that go hand in hand with aeronautical application. Thus, the preparation of aviation fuels in the refinery is based on a narrow distillation range and high octane numbers. These bases are generally constituted by alkylate, reformed and isopentane sections, the latter being used at low concentrations due to their high volatility.

But before they are marketed, aviation fuels must satisfy other precise physicochemical characteristics defined by international specifications. Thus, aviation fuels must have low vapor pressure to avoid vaporization (vapor blockage) problems at low pressures found at altitude and for obvious safety reasons. The distillation end point should be somewhat low to limit deposit formations and their harmful consequences (loss of energy, impaired cooling).

They should also have a high net calorific value (LCV) to ensure the best possible range. In addition, as aviation fuels are used in engines that perform well and often operate at high load, that is, under near-hit conditions, this type of fuel is expected to have good resistance to spontaneous combustion. In addition, for aviation fuel, two characteristics that are comparable to octane numbers are determined: one, the MON, or engine octane number, related to operating with a slightly weak mixture (cruising power), the other, the Number of Performance or PN, related to use with a distinctly strong mix (takeoff).

In order to ensure the high octane requirements at the aviation fuel production stage, the refiner generally adds an organic lead compound and more particularly tetraethyl lead (TEL). As with land vehicle fuels, administrations tend to lower the lead content or even ban this additive because it is harmful to health and the environment. Thus, the elimination of lead from aviation fuel composition is becoming a long or medium term goal.

To replace lead additives, solutions have been proposed in the literature such as, for example, adding other additives or components. WO 02/227/66 describes a unleaded aviation fuel including a hydrocarbon compound that can be tryptane combined with at least one saturated liquid (4 to 10C) aliphatic hydrocarbon compound (the base thus obtained is not a AVGAS base) and also including an alkyl ether. The problem of preparing AVGAS aviation fuels with good combustion characteristics has not been resolved. US Patent 2,398,197 (1943) describes an aniline or alkyl aniline-containing aviation fuel in which ratios of approximately 0.5 to 10% asymmetric alkyl ketone are incorporated. However, the problem of the invention was not solved, since AVGAS was known only since 19501960.

In EP 697 033 aromatic amine is added to a unleaded aviation fuel consisting of isopentane, alkylate and toluene.

In EP 910 617, a mixture of aromatic amine and an alkyl tert-butyl ether and optionally a manganese compound is added to a broad boiling range alkylate constituting the aviation fuel. EP 609 089 describes alkylate-based unleaded aviation fuels to which an ether such as ETBE or MTBE is added, as well as 0.4 to 0.5 g / gallon manganese as cyclopentadienyl tricarbonyl compounds manganese. The problem of the invention has not been addressed as the fuel described is not base type AVGAS: it includes alkylates but does not include reformed or isomerates.

In other patents such as EP 540 297 and EP 609 089 Methylcyclopentadienyl Manganese Tricarbonyl (MMT) is added to aviation fuel as a substitute for lead.

Even if these documents seem to show that these additives lead to an increase in octane number, that increase remains insufficient. It is not shown whether the characteristics of the aviation fuel thus obtained meet other requirements related to calorific value, vapor pressure and distillation range. Moreover, the compatibility of these different additives with respect to the environment has not been proven.

Other patents, such as EP 948 584, propose to act on the composition of hydrocarbon bases and in particular by the addition of tryptane in the aviation fuel composition. But the use of such oil-free bases, in addition to price, creates technical difficulties in storing and logistics of these bases for the refiner, generating costs beyond those usually obtained for formulating a standard aviation fuel from a blend of hydrocarbon bases available at the refinery.

In addition, the use of additives to replace lead compounds to improve octane number is well known for land vehicle gasolines, as in EP 474 342, GB 2 114 596, US 5,032,144 or US 4,647,292. However, aviation fuel is subject to much stricter standards than ground vehicle gasoline for reliability and operational safety during takeoff and at altitude. Thus, it is not so simple to use these aviation fuel additives as there are far more severe restrictions than those required for automobile gasolines.

SUMMARY OF THE INVENTION

To meet these pressing needs of choice, the invention relates to a novel unleaded aviation fuel composition for piston engine or reciprocating aircraft produced from hydrocarbon bases that are generally available in an oil refinery, having a high octane number, in which the organic lead compounds have been replaced by different additives to increase their octane number. It relates in particular to aviation fuels whose VCN (net calorific value), vapor pressure, MON and distillation cut characteristics are as close as possible to the specifications adopted for AVGAS 100LL and described in ASTM D910-4, in addition to lead content.

To this end, a subject of the invention is a unleaded aviation fuel composition having a MON of greater than 100 including a large proportion of AVGAS base type fuel and a small proportion of at least two esters of the ester group. with at least one mono or polycarboxylic acid and at least one alcohol or polyol; by anhydrides with at least one mono or polycarboxylic acid; by aromatic ethers having a content exceeding 5% by weight and consisting of ketones containing more than 10% by weight and mixtures thereof. The composition of the unleaded aviation fuel which is the subject of the invention has a sufficiently high octane number of at least 100, a VCN extremely close to 43.5 MJ / kg, preferably greater than that, and a vapor pressure at 37.8 ° C preferably ranging from 38 to 49 kPa and is obtained from a mixture of hydrocarbon bases available in sufficient quantities from the refinery and containing additives.

DETAILED VERSION DESCRIPTION

By AVGAS is meant a mixture of refined bases such as alkylates originating, for example, from the process of alkylating isobutane by light olefins, the reformed ones originating from the reforming of ordinary gasolines and isopentane.

A small proportion is, for example, between 1 and 40% by weight of the weight of the composition.

The advantages of the invention which will be described more precisely below are linked, on the one hand, to the optimal choice of the mixture of AVGAS-type hydrocarbon bases containing the highest octane number while meeting the stated specifications for VCN, vapor pressure and distillation cut, and the best conciliation of component mix also having the best MON, the best VCN, the best vapor pressure (VP) and an AVGAS-compatible base distillation cut, the addition of the mixture of oxygenated components having to degrade the characteristics of the AVGAS base type mixture itself as little as possible.

For the purpose of carrying out the invention, esters are obtained from at least one saturated mono- or dicarboxylic acid containing from 1 to 10 carbon atoms and preferably from 1 to 6 carbon atoms with at least one alcohol or polyol containing 1 or 10 carbon atoms.

Anhydrides are obtained from mono or dicarboxylic acids containing from 1 to 10 carbon atoms, which may be cyclic or linear, optionally substituted by straight, branched or cyclic alkyl groups.

The ethers contain at least one aromatic ring substituted by at least one ether group including from 1 to 10 carbon atoms.

Ketones include from 3 to 10 carbon atoms per straight carbon chain, optionally substituted by alkyl groups in linear, branched or cyclic form.

Using these components alone or in the mixture it is advantageously possible to introduce into the aviation fuel composition according to the invention up to 30% by weight of at least two such components.

Preferably to ensure compliance with the required specifications for aviation fuel according to the invention, the ester content of the aviation fuel composition ranges from 5 to 30 wt% and more preferably from 10 to 20 wt% by weight. a mixture with another component.

Also, the anhydride content is chosen to be greater than 5% by weight of the composition, and preferably ranges from 5 to 25% by weight.

Preferably to satisfy the characteristics of the composition according to the invention, the aromatic ether content ranges from 5 to 30% by weight and more preferably from 5 to 15% by weight in a mixture with a second component.

With respect to the addition of ketone to the composition, its composition is chosen to be greater than 10% by weight of the composition and preferably ranging from 10 to 25% by weight.

In order to carry out the invention and in particular optimize the MON value, at least two different components in nature, chosen from the list of components of the invention, are advantageously mixed, preferably 5 to 25% by weight of the composition of a first compound and 25 to 25%. 5% by weight of a second compound, such proportions may vary by the addition of a third compound.

In a preferred embodiment of the invention, less than 3.5% by weight of at least one optionally alkyl substituted aromatic amine, preferably 0.5 to 3% by weight, may be introduced into the fuel composition. Advantageously such aromatic amine includes at least one amino group attached to at least one aromatic ring, optionally substituted by at least one alkyl of 1 to 10 carbon atoms.

Among the compositions according to the invention, compositions comprising 25 to 30 wt% of at least one ester, anhydride, ketone or ether type compound in combination with 0.5 to 3 wt% aromatic amine are preferred.

More advantageously, to produce the combinations of the invention, the nature of the compounds is chosen as described below.

The esters of the invention are chosen from alkyl carboxylates whose alkyl groups include from 1 to 6 carbon atoms, preferably methyl, ethyl, propyl, butyl, dimethyl, diethyl, isopropyl, isobutyl and tert-butyl acetates, propionates, butyrates, pentanoates and carbonates; with tert-butyl acetate, methyl pivalate and diethyl carbonate being most particularly preferred.

The anhydrides of the invention are chosen from acetic, propionic, butyric, valeric acid anhydrides, but also malic and succinic acid anhydrides; with pivalic anhydride being preferred.

The aromatic ethers according to the invention are chosen from the group consisting of alkyl aryl ethers such as alkyl phenyl ethers, diaryl ethers, alkyl groups including from 1 to 10 carbon atoms in straight or branched form. Preferred ethers are methylphenyl ether or anisol, ethylphenyl ether or phenethol, propylphenyl ether, butylphenyl ether, isopropylphenyl ether, isobutylphenyl ether; with phenetol being more particularly preferred.

The ketones according to the invention are chosen from the symmetrical or asymmetric alkyl ketones from the group consisting of dimethyl ketone, diethyl ketone, dipropyl ketone, dibutyl ketone, diisobutyl ketone, dipentyl ketone, methylpropyl ketone, methylpropyl ketone, methylbutyl ketone, methylbutyl ketone ethylbutyl ketone, ethylisobutyl ketone, probylbutyl ketone, propylisobutyl ketone, isoprobilbutyl ketone; with methylisobutyl ketone being preferred.

When, according to various variables, the composition according to the invention contains a substituted aromatic alkyl amine, the latter is chosen from amines including 1 to 5 carbon atoms per carbon chain and at least one aromatic ring substituted by the least one alkyl including from 1 to 5 carbon atoms in ortho (o), meta (m) or para (p) position relative to the amine. This aromatic amine is chosen from phenylamine, o, m, p-tert-butylphenylamines, o, m, p-methylphenylamines, o, m, p-ethylphenylamines, o, m, p-propylphenylamines, o, m, p-isopropylphenylamines , o, m, p-isobutylphenylamines, 3,5-dimethylphenylamine, 3,4 dimethylphenylamine, 3,5 diethylphenylamine, 3,5-diethylphenylamine, 3,5 dipropylphenylamine, 3,4-dipropylphenylamine, 3,5-methylethylphenylamine, 3, 4-methylethylphenylamine. Preferred amines are 3,5-dimethylphenylamine, 3,4-dimethylphenylamine, p-methylphenylamine, m-methylphenylamine or m-toluidine, p-ethylphenylamine, m-ethylphenylamine, m-isopropylphenylamine and em-tert-butylphenylamine; with m-toluidine being more particularly preferred.

Advantageously, the aviation fuel-based composition includes from 25 to 80% by weight of an aviation alkylate, 30 to 5% by weight of aviation retired and 5 to 25% by weight of isopentane.

An aviation alkylate includes at least 95% by weight of isoparaffins, ideally at least 98.5% by weight, including at least 65% by weight of C8-isoparaffins, ideally at least 70% by weight, containing in particular particularly at least 60% by weight, the ideal being at least 70% by weight of a trimethylpentane mixture, the latter being at least 40% by weight, preferably 40 to 65% by weight, the ideal being at least 52% by weight consisting of by 2,2,4 and 2,3,3 trimethylpentane, the weight ratio of which may vary depending on the manufacturing process from 2/1 to 8/1.

An aviation pensioner is generally comprised of a hydrocarbon cut containing at least 70% by weight, ideally at least 85% by weight, aromatics essentially consisting of toluene (35 to 75% by weight, preferably 45 to 70% by weight). C8 aromatics (15 to 50% by weight ethylbenzene and ortho, meta, para-xylene) and C9 aromatics (5 to 25% by weight propylbenzene, methylethylbenzenes and trimethylbenzenes), the absolute contents and relative proportions of the different components may vary with cutoff points, the nature of the raw material sent for reform, the type of catalyst used and the operating conditions of the reform.

As already indicated, the scope of the invention would not be exceeded if the amounts of toluene and isooctane required to adjust the characteristics of the mixture were added to the AVGAS-type base mixture, in particular MON, VCN, vapor pressure (VP) and cut-off. distillation. The scope of the invention would not be exceeded if, for certain compositions with or without aromatic amine according to the invention, a lead alkyl derivative was added to a maximum of 0.14 g of lead and preferably 0.08 g of lead per liter. aviation fuel, eg in the form of detraethyl lead to achieve in particular the minimum take-off PN (performance number).

Lead levels are cited as reference to the methods for measuring lead levels described in ASTM D2392.

Similarly, the scope of the invention would not be exceeded if 5% to 20% of mono or dialkyl ethers such as diisopropyl ether, ethyl tert-butyl ether, methyl tert-butyl ether, dimethyl ether and tert-amyl methyl ether were added to the mixtures according to the invention. Of course, to satisfy the other required characteristics, the aviation fuel according to the invention may contain one or more additives that a skilled person can easily choose from among the various additives used in standard aviation fuels. Particular mention should be made, but not limitation, of additives such as antioxidants, antifreeze agents, antistatic additives, corrosion inhibitors / enhancers, dyes and mixtures thereof.

In the remainder of the present description, examples are given by way of illustration, but should not be construed as limiting the scope of the present invention. EXAMPLE The present example is intended to show that, starting with the compounds according to the invention only, taken two by two or in a mixture with an aromatic amine, at the concentrations claimed in the present invention, it is possible to produce aviation fuels of the same type. AVGAS whose specifications correspond to those required by ASTM 910-4. The operation is performed with one or two bases B1 and B2 whose composition is shown in Table I below.

TABLE I • VP: Fuel Vapor Pressure ♦ PN: Fuel Performance Number or Performance Number determined on a CPR engine according to ASTM D909 (F4) * VCN: Net calorific value whose minimum target level for AVGAS 100LL is 43.5 MJ / kg. Various mixtures of compounds were tested on B1 and B2. Each test is referenced Xi in Table II below.

TABLE II

Thus it is noted that it is possible to obtain unleaded aviation fuels with characteristics similar to AVGAS 100LL aviation fuels by adding the oxygenated additives according to the invention by the standard bases.

In fact, mixtures that appear to be out of specification with respect to VP (38-49 kPa) can easily be corrected by optimizing the base composition. The PN may reach values greater than 130 and the VCN may approach the specification by approximately 10%.

Thus, the results show that it is possible, by acting on the different parameters, to optimize the compositions to achieve the intended objective, which is not evident in relation to previously known models, which do not mention values of PN, VCN or VP simultaneously.

Furthermore, it is shown that the addition of lead does not always have a positive effect on the performance of the fuels thus obtained.

Claims (23)

1. “Lead-free aviation fuel composition”, characterized in that it contains MON greater than 100, including a large proportion of Avgas base type fuel, between 1 and 40% by weight of at least two oxygenated compounds of a different chemical nature; from the group consisting of esters with at least one mono or polycarboxylic acid and at least one alcohol or polyol, anhydrides with at least one mono or polycarboxylic acid; by aromatic ethers having a content exceeding 5% by weight and consisting of ketones containing more than 10% by weight and mixtures thereof, said ester is obtained from monounsaturated or dicarboxylic acids including 1 to 10 carbon atoms and preferably 1 to 6 carbon atoms with an alcohol including from 1 to 10 carbon atoms, said anhydride is obtained from mono or dicarboxylic acids, containing from 1 to 10 carbon atoms, which may be cyclic or linear, optionally substituted by groups. straight, branched or cyclic alkyl, said ether including at least one aromatic ring substituted by at least one ether group including from 1 to 10 carbon atoms, said ketone including from 3 to 10 carbon atoms per linear carbon chain optionally substituted by straight, branched or cyclic alkyl groups. "Composition" according to Claim 1, characterized in that the ester is obtained from saturated dicarboxylic mono acids comprising 1 to 6 carbon atoms with an alcohol of 1 to 10 carbon atoms. "Composition" according to Claim 1, characterized in that it contains up to 30% of at least two compounds in aviation fuel. "Fuel composition" according to any one of the preceding claims, characterized in that the ester content ranges from 5 to 30%. "Fuel composition" according to any one of the preceding claims, characterized in that the anhydride content ranges from 5 to 25%. "Fuel composition" according to any one of the preceding claims, characterized in that the aromatic ether content ranges from 5 to 30% by weight and more preferably from 5 to 15% by weight in a mixture with at least one second compound. . "Fuel composition" according to any one of the preceding claims, characterized in that the ketone content ranges from 10 to 25% by weight. "Fuel composition" according to any one of the preceding claims, comprising from 5 to 25% by weight of a first oxygenated compound and 25 to 5% by weight of a second oxygenated compound other than the first oxygenated compound; said first oxygenated compound and said second oxygenated compound being as defined in claim 1. "Fuel composition" according to any one of the preceding claims, characterized in that it contains less than 3.5% of at least one optionally substituted alkyl aromatic amine, preferably from 0.5 to 3% by weight. "Fuel composition" according to claim 9, characterized in that the aromatic amine includes at least one amino group attached to at least one aromatic ring, optionally substituted by at least one alkyl of 1 to 10 carbon atoms. "Fuel composition" according to any one of the preceding claims, characterized in that it contains 25 to 30% by weight of at least two ester, anhydride, ketone or ether type compounds in combination with 0.5 to 3% by weight. weight of aromatic amine. "Fuel composition" according to any one of the preceding claims, characterized in that the ester chosen is methyl, ethyl, propyl, butyl, dimethyl, diethyl, isopropyl, isobutyl and teriobutyl acetates, propionates, butyrates, pentanoates and carbides; tert-butyl acetate, methyl pivalate and diethyl carbonate being preferred. "Fuel composition" according to any one of the preceding claims, characterized in that the anhydride is chosen from acetic, propionic, butyric, valeric acid anhydrides, but also malic and succinic acid anhydrides; pivalic anhydride being preferred. "Fuel composition" according to any one of the preceding claims, characterized in that the ether is selected from the group consisting of diaryl ethers and alkylphenyl ethers, and the alkyl group comprising from 1 to 10 carbon atoms in a linear or non-linear manner. It is preferably branched, preferably methylphenyl ether or anisol, ethylphenyl ether or phenethol, propylphenyl ether, butylphenyl ether, isopropylphenyl ether, isobutylphenyl ether, with phenetol being more particularly preferred. "Fuel composition" according to any one of the preceding claims, characterized in that ketone is selected from the symmetrical or asymmetric alkyl ketones from the group consisting of dimethyl ketone, diethyl ketone, dipropyl ketone, dibutyl ketone, diisobutyl ketone, dipentyl ketone, methyl ethyl ketone. methylpropyl ketone, ethylpropyl ketone, methylbutyl ketone, methylisobutyl ketone, ethylbutyl ketone, ethylisobutyl ketone, probilbutyl ketone, propylisobutyl ketone, isoprobilbutyl ketone; methylisobutyl ketone being preferred. "Fuel composition" according to Claim 10, characterized in that the aromatic amine is selected from the group consisting of amines including 1 to 5 carbon atoms per carbon chain and at least one aromatic ring substituted by at least one alkyl. including from 1 to 5 carbon atoms in the ortho (o), meta (m) or to (p) position relative to the amine. "Fuel composition" according to Claim 16, characterized in that the aromatic amine is selected from the group consisting of phenylamine, o, m, p-tert-butylphenylamines, o, m, p-methylphenylamines, o, m , p-ethylphenylamines, o, m, p-propylphenylamines, o, m, p-isopropylphenylamines, o, m, p-isobutylphenylamines, 3,5-dimethylphenylamine, 3,4-dimethylphenylamine, 3,5-diethylphenylamine, 3,4 -diethylphenylamine, 3,5-dipropylphenylamine, 3,4-dipropylphenylamine, 3,5-methylethylphenylamine, 3,4-methylethylphenylamine. "Fuel composition" according to Claims 16 and 17, characterized in that the amines chosen are p-methylphenylamine, m-methylphenylamine or m-toluidine, p-ethylphenylamine, m-ethylphenylamine, m-isopropylphenylamine and m-tert-amine. butylphenylamine, m-toluidine being preferred. "Fuel composition" according to any one of the preceding claims, characterized in that said aviation fuel-based fuel comprises from 25 to 80% by weight of an aviation alkylate, 30 5% by weight of aviation retired. and 5 to 25% by weight of isopentane. "Fuel composition" according to any one of the preceding claims, characterized in that said aviation fuel-based reforming contains more than 35% by weight of toluene, preferably between 45 and 70% by weight. "Fuel composition" according to any one of the preceding claims, characterized in that said aviation fuel-based alkylate contains more than 40% by weight of 2,2,4 and 2,3,3 trimethylpentanes, preferably 40 to 65% by weight. "Fuel composition" according to any one of the preceding claims, characterized in that a lead alkyl derivative is added to a maximum of 0.14 per lead per liter of aviation fuel, preferably up to 0.08g. "Fuel composition" according to any one of the preceding claims, characterized in that it contains from 5% to 20% mono or dialkyl ethers such as diisopropyl ether, ethyl tert-butyl ether, methyl tert-butyl ether. dimethyl ether and tert-amyl methyl ether.