EP2303997B1 - Aviation gasoline for piston engines of aircraft, preparation process thereof - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to a composition of aviation gasoline (AVGAS) lead-free and oxygen-free, for aircraft with piston or reciprocating engines. In particular, the subject of the present invention is an unleaded aviation gasoline with an octane number MON F2 greater than or equal to 91 and having very good combustion characteristics.

BACKGROUND

Aviation gasoline is a carefully crafted product subject to stringent regulations that go hand in hand with any aeronautical application. Thus, the refinery preparation, aviation gasolines, is carried out with bases characterized by both a narrow distillation range and high octane numbers. These bases are generally constituted by alkylates, reformates and / or isopentane sections, the latter being used in low concentration because of their high volatility.

• * une faible tension de vapeur (inférieure à 490mbar) afin d'éviter les problèmes de vaporisation (vapor lock) ou risques de givrage accrus par les basses températures rencontrées en altitude ;
• * un point final de distillation inférieur à 170 °C, pour limiter les formations de dépôts et leurs conséquences néfastes (pertes de puissance, refroidissement détérioré) ;
• * une bonne tenue au froid (absence de cristaux jusqu'à -58 °C) pour empêcher tout colmatage des filtres et des canalisations en altitude ;
• * une faible teneur en soufre, actuellement limitée à 0,05 % en poids,

toutes ces caractéristiques étant réunies dans la norme ASTM D 910-07 en vigueur à la date de dépôt de la présente demande de brevet.Before being placed on the market, aviation gasolines must meet other specific physico-chemical characteristics defined by international specifications. Thus, aviation gasolines must present

• * a low vapor pressure (less than 490mbar) to avoid vaporization problems (vapor lock) or increased icing risks due to the low temperatures encountered at altitude;
• * a distillation end point of less than 170 ° C, to limit deposits formation and their adverse consequences (power losses, deteriorated cooling);
• * good cold resistance (absence of crystals down to -58 ° C) to prevent clogging of filters and pipes at altitude;
• a low sulfur content, currently limited to 0.05% by weight,

all of these features being included in ASTM D 910-07 in effect on the filing date of this patent application.

Aviation gasolines are used on engines offering good performance and frequently operating at high load, that is to say in conditions close to knocking. It is therefore necessary that this type of fuel has a very good resistance to auto-ignition.

For aviation gasoline, the engine octane number or MON is determined relative to the slightly lean mixture operation (cruising speed). In order to guarantee this requirement in high octane, the refiner generally proceeds, at the stage of manufacturing aviation gasoline, with the addition of an organic lead compound, and more particularly tetraethyl lead (TEP). However, as for gasoline for land vehicles, government authorities tend to lower the lead content, or even to remove this additive, because of its harmful nature for the environment and health. Thus, first of all, the reduction and elimination of lead from the aviation gasoline composition become an objective to be achieved in the short and medium term.

The use of additives to replace lead compounds to improve the octane number is well known for terrestrial vehicle species, as in the US Pat. EP 474,342 , GB 2,114,596 , US 5,032,144 or US 4,647,292 . Since aviation gasoline is subject to much more stringent regulations than gasoline for land vehicles, for reasons of reliability and operational safety during the take-off phase and at altitude, it is not easy to use these additives for aviation gasoline, for which the constraints are much harder than those required for automotive gasolines.

With regard to aviation gasoline, in order to replace lead additives, solutions have been proposed in the literature, for example by adding other additives or components, such as aromatic amines, for example aniline, alkylanilines, methylcyclopentadienyl manganese tricarbonyl (MMT).

EP 540 297 and EP 609 089 propose adding methylcyclopentadienyl manganese tricarbonyl (MMT) to aviation gasoline as a substitute for lead.

In EP 609 089 described are lead-free aviation gasolines based on alkylates, in which an ether such as ETBE or MTBE is added as well as 0.4 to 0.5 g / gallon of manganese in the form of cyclopentadienyl manganese compounds. tricarbonyl. The problem of the invention was not discussed since the gasoline described is not an AVGAS type base: it comprises alkylates, but does not include reformates or isomerate compounds.

In EP 697,033 , is described a lead-free aviation gasoline consisting of isopentane, alkylate, toluene of MON between 90 and 93 additivated with 4 to 20% of an aromatic amine to obtain a gasoline MON more than or equal to 98.

EP 910617 discloses a mixture of aromatic amine and alkyltertiobutylether, and optionally a manganese compound which is added to a broad-boiling alkylate constituting aviation gasoline.

In WO 02/22766 a lead-free aviation gasoline comprising a hydrocarbon compound which may be triptane associated with at least one saturated, liquid aliphatic hydrocarbon compound (4 to 10 ° C) and further comprising an alkyl ether (the base thus obtained is not an AVGAS base).

Even if these additives lead to an increase in the octane number, this increase sometimes remains insufficient. In addition, the addition of these additives does not always meet the other requirements specific to aviation gasoline, such as calorific value, vapor pressure and distillation range.

Moreover, these various additives are not always compatible with respect for the environment. For example, aromatic amines widely used to improve the octane number are all classified toxic substances, in case of absorption by inhalation or ingestion and especially on the skin. Methylcyclopentadienyl manganese tricarbonyl (MMT) is, for its part, indexed by the EPA as an air pollutant, which may represent potential hazards for humans. Oxygen compounds are not currently permitted in aviation gasoline compositions.

• EP 948 584 propose une essence aviation de MON supérieur à 98 qui contient au moins 30 % en volume de triptane et/ou de 2,2,3-triméthylpentane.

This is why other technical solutions without additives have been proposed:

• EP 948 584 proposes an aviation fuel of MON greater than 98 that contains at least 30% by volume of triptane and / or 2,2,3-trimethylpentane.

EP 1 359 207 discloses a composition of unleaded automotive gasoline MON between 80 and 98 containing from 5 to 25% by volume triptane and / or 2,2,3-trimethylpentane, from 5 to 15% by olefins, from 15 to 35% of aromatics and 40 to 65% of C4-C12 paraffins.

EP 1 224 247 describes a lead-free gasoline usable in particular as aviation fuel of MON of at least 80, of RON between 90 and 115 containing a C8-C12 alkane with at least 4 branches methyl and / or ethyl. Preferably, the preferred species further comprises triptane and / or 2,2,3-trimethylpentane.

But the addition in large quantities of compounds such as triptane and / or 2,2,3-trimethylpentane or alkanes with at least 4 branches which are very minor in the usual oil bases from refineries, and requires not only processes of separation and purification expensive to synthesize these compounds but also generates for the refiner technical difficulties of storage and additional logistics for these compounds generating higher costs than those generally obtained to formulate a conventional aviation gasoline from a mixture of hydrocarbon bases usually available in refineries.

WO 04/044106 discloses unleaded aviation gasoline compositions of MON ranging from 92 to 98 and containing 10 to 90% by volume of at least one trimethylpentane and at least one C4-C5 paraffin. An example of a gasoline composition according to the invention of MON 95 comprises 59% of isooctane, 8% of toluene, Isopentane 24% by volume of alkylate and 16% of alkylate fraction other than isooctane.

DE 197 44 109 discloses an unleaded gasoline composition for 2 and 4 stroke engines comprising 70-85% by volume of C 8 isoparaffins, 17-19% by volume of C 5 isoparaffins, 2-4% of C 6 isoparaffins and preferably not more than 0.5% aromatics and 0.1% benzene. This reference does not specify whether this gasoline may be suitable as aviation gasoline.

WO 00/77130 discloses a composition of aviation fuels.

SUMMARY OF THE INVENTION

In order to meet these needs of an AVGAS type lead-free and oxygen-free aviation gasoline, the invention therefore aims at a novel composition of lead-free aviation gasoline, intended for aircraft with reciprocating or reciprocating engines, made from bases hydrocarbon products generally available in a petroleum refinery, having a high octane number. The invention aims in particular aviation gasolines whose characteristics of PCI (lower heating value), vapor pressure (TV) and distillation cup, meet the specifications for aviation gasoline grades described in ASTM D910- 07, except lead content and engine performance.

For this purpose, the subject of the invention is an aviation gasoline composition as defined in claim 1.

The aviation gasoline composition according to the invention can be obtained simply and economically from a mixture of hydrocarbon bases usually available in the refinery.

• un MON supérieur ou égal à 91, de préférence supérieur ou égal à 92, et inférieur ou égal à 95,
• un RON (indice d'octane recherche) supérieur ou égal à 95, de préférence supérieur ou égal à 96, avantageusement supérieur ou égal à 98, et inférieur ou égal à 100,
• un PCI supérieur ou égal à 43,4, de préférence supérieur ou égal à 43,5, et avantageusement supérieur ou égal à 43,53 MJ/kg,
• une tension de vapeur à 37,8°C variant de préférence entre 38 et 49 kPa, de préférence entre 38,6 et 48,4 kPa,

This composition has the following characteristics:

• a MON greater than or equal to 91, preferably greater than or equal to 92, and less than or equal to 95,
• an RON (research octane number) greater than or equal to 95, preferably greater than or equal to 96, advantageously greater than or equal to 98, and less than or equal to 100,
• an ICP greater than or equal to 43.4, preferably greater than or equal to 43.5, and advantageously greater than or equal to 43.53 MJ / kg,
• a vapor pressure at 37.8 ° C preferably varying between 38 and 49 kPa, preferably between 38.6 and 48.4 kPa,

DETAILED DESCRIPTION OF THE INVENTION

The invention firstly relates to an aviation gasoline composition defined in claim 1.

This composition presents
a MON greater than or equal to 91, preferably greater than or equal to 92, and less than or equal to 95,
an RON greater than or equal to 95, preferably greater than or equal to 96, advantageously greater than or equal to 98, and less than or equal to 100,
an ICP greater than or equal to 43.4, preferably greater than or equal to 43.5, and advantageously greater than or equal to 43.53 MJ / kg,
a vapor pressure at 37.8 ° C preferably varying between 38 and 49 kPa, preferably between 38.6 and 48.4 kPa

For the purposes of the present invention, the term gasoline without oxygenated compound aviation gasoline containing no oxygenated compound of alcohol type, ester or ether except ispopropanol used as an anti-ice agent in an amount less than or equal to 1% of the volume total gasoline.

The aviation gasoline composition according to the invention comprises
from 14 to 22% by volume of isopentane,
from 30 to 40% by volume of isooctane,
from 8 to 20% by volume of aromatics,
of which 4 to 9% by volume of toluene.

In a particularly advantageous manner, the aviation gasoline composition according to the invention comprises
from 20 to 22% by volume of isopentane,
from 30 to 32% by volume of isooctane, preferably from 31 to 32%,
from 15 to 18% by volume of aromatics, preferably 7 to 9% by volume of toluene.

The subject of the invention is also a process for the preparation of the composition defined above.

The process according to the invention consists in mixing at least one isopentane cut B1, at least one base of aviation alkylate type B2 and at least one base of aviation reformate type B3.

Isopentane cuts and aviation alkylate, aviation reformate bases are hydrocarbon bases readily available in refineries.

• ▪ 10 à 20 % en volume d'au moins une coupe isopentane B1 qui est une base légère appartenant à la famille des hydrocarbures paraffiniques constituée essentiellement d'isoparaffines en C4 et/ou C5 et comprenant de préférence au moins 80 % en volume, avantageusement au moins 90 % en volume d'isoparaffines en C4 ou C5. Selon un mode de réalisation préférée, la base B1 comprend au moins 90 % en volume d'isopentane, et avantageusement au moins 95 %; les bases isopentane B1 ne contiennent en général pas plus de 1 % en volume d'oléfines ; ces bases légères paraffiniques peuvent par exemple provenir de fractions les plus légères de distillat produit par distillation atmosphérique de pétrole brut et/ou issues d'unités d'isomérisation d'alcanes ;
• ▪ 62 à 88 % en volume d'au moins une base alkylat aviation B2 constituée essentiellement d'isoparaffines comprenant 6 à 9 atomes de carbone et de préférence au moins 90 % en volume d'isoparaffines comprenant 6 à 9 atomes de carbone; les alkylats aviation comprennent en général au moins 95%, de préférence au moins 98,5% en volume d'isoparaffines, dont au moins 65%, de préférence au moins 70%, et avantageusement au moins 80 % en volume d'isoparaffines en C8 ; selon un mode de réalisation préféré, les bases alkylat B2 comprennent au moins 45 %, de préférence au moins 48 % en volume d'isooctane, et avantageusement au moins 30 %, de préférence au moins 34 % en volume des autres isoparaffines en C8 ; ces bases alkylat aviation peuvent provenir de différents procédés de traitement de pétrole brut, généralement présents dans les raffineries ; les bases B2 sont en général issues du procédé d'alkylation de l'isobutane par des oléfines légères ;
• ▪ 1 à 22 % en volume d'au moins une base de type réformat aviation B3 constituée essentiellement d'(alkyl)aromatiques (ou simplement aromatiques) ; les bases réformat sont en général issues du réformage des essences de distillation directe et l'isopentane ; les réformats aviation sont généralement constitués d'une coupe hydrocarbonée contenant au moins 70%, de préférence au moins 85%, en volume d'aromatiques comprenant du toluène (en général de 35 à 75%, de préférence 45 à 70% ,en volume), d'alkylaromatiques en C8 (en général de 15 à 50% en poids d'éthylbenzène, et d'ortho, méta, para-xylène) et d'alkylaromatiques en C9 (en général de 5 à 25% en poids de propylbenzène, méthyléthylbenzènes et triméthylbenzènes), les teneurs absolues et proportions relatives des différents composants pouvant varier avec les points de coupe, la nature de la charge envoyée au réformage, le type de catalyseur utilisé et les conditions opératoires du réformage ; de manière préférentielle, les bases alkylats aviation B3 mises en oeuvre dans le cadre de la présente invention contiennent moins de 1 % en volume de benzène ; outre les composés aromatiques, les bases réformats B3 peuvent notamment contenir des paraffines, iso et n-paraffines, en général présentes en quantité inférieure ou égale à 5 % en volume.

The process according to the invention consists in mixing

• ▪ 10 to 20% by volume of at least one isopentane cut B1 which is a light base belonging to the family of paraffinic hydrocarbons consisting essentially of C4 and / or C5 isoparaffins and preferably comprising at least 80% by volume, advantageously at least 90% by volume of isoparaffins C4 or C5. According to a preferred embodiment, the base B1 comprises at least 90% by volume of isopentane, and advantageously at least 95%; the isopentane bases B1 generally contain not more than 1% by volume of olefins; these light paraffinic bases may for example come from the lightest fractions of distillate produced by atmospheric distillation of crude oil and / or from isomerization units of alkanes;
• ▪ from 62 to 88% by volume of at least one aviation alkylate base B2 consisting essentially of isoparaffins comprising 6 to 9 carbon atoms and preferably at least 90% by volume of isoparaffins comprising 6 to 9 carbon atoms; the aviation alkylates generally comprise at least 95%, preferably at least 98.5% by volume of isoparaffins, of which at least 65%, preferably at least 70%, and advantageously at least 80% by volume of isoparaffins, C8; according to a preferred embodiment, the alkylate bases B2 comprise at least 45%, preferably at least 48% by volume of isooctane, and advantageously at least 30%, preferably at least 34% by volume of the other C 8 isoparaffins; these aviation alkylate bases can come from different crude oil processing processes, generally present in refineries; B2 bases are generally derived from the process of alkylation of isobutane with light olefins;
• ▪ 1 to 22% by volume of at least one B3 aviation reformate base consisting essentially of (alkyl) aromatic (or simply aromatic); the reformate bases are generally derived from the reforming of the direct distillation species and isopentane; the aviation reformates generally consist of a hydrocarbon fraction containing at least 70%, preferably at least 85%, by volume of aromatics comprising toluene (in general from 35 to 75%, preferably from 45 to 70% by volume ), C8 alkylaromatic (generally 15 to 50% by weight ethylbenzene, and ortho, meta, para-xylene) and C9 alkylaromatic (generally from 5 to 25% by weight of propylbenzene, methylethylbenzenes and trimethylbenzenes), the absolute contents and relative proportions of the various components being able to vary with the cutting points, the nature of the feedstock sent to the reforming, the type of catalyst used and the operating conditions reforming; preferably, the aviation alkyl bases B3 used in the context of the present invention contain less than 1% by volume of benzene; in addition to the aromatic compounds, the B3 reformate bases may in particular contain paraffins, iso and n-paraffins, generally present in an amount of less than or equal to 5% by volume.

For the purposes of the present invention, the base Bi is "essentially composed of the compounds ...." means that said compounds ... represent at least 70% of the volume of said base Bi.

It would not be departing from the scope of the invention if the required quantities of toluene and / or isooctane and / or isopentane were added to the mixture of bases B1, B2 and B3 described above in order to adjust the characteristics of the composition of the composition. gasoline, in particular MON, PCI, vapor pressure (TV) and distillation cut.

Nor would it be possible to extrapolate the invention by adding other bases resulting from conventional refining operations (for example distillation of crude oil, catalytic cracking, hydrocracking, reforming processes, isomerization , alkylation, ....) and / or synthetic hydrocarbons such as in particular those obtained by oligomerization of olefins, by Fisher-Tropsch synthesis, by BTL (biomass to liquid) type processes, CTL (gas to liquid) and / or GTL (gas to liquid) from materials of natural and / or synthetic origin, of animal and / or plant and / or fossil origin.

Each base or cup used in the composition of the gasoline according to the invention, ie the bases B1 to B3 as well as any additional base, may have undergone, in all or in part, a desulfurization and / or denitrogenation treatment and possible dearomatization at any stage of its elaboration. For example, bases which have been hydrotreated under more or less severe conditions (including hydrosulfuration and / or saturation of aromatic and olefinic compounds and / or hydrodeazotation) may be used.

The aviation gasoline according to the invention advantageously has a sulfur content (measured according to ASTM standard D1266 or ASTM D2622 ° less than or equal to 500 ppm, preferably less than or equal to 100 ppm, or even lower than or equal to 50 ppm, and even more preferably less than or equal to 10 ppm.

In order to satisfy the characteristics set, for example, by the ASTM D 910-07 standard, the aviation gasoline according to the invention may contain one or more additives, which the person skilled in the art will be able to easily choose from the numerous additives conventionally employed for the species. aviation. These include, but in a way non-limiting additives such as antioxidants, anti-ice, antistatic additives, corrosion inhibitors / lubricant enhancers, cold properties improvers, tracer additives, dyes, detergents and mixtures thereof.

These additives are generally incorporated into the gasoline in amounts of less than 1000 ppm. For the purposes of the present invention, if one or more of the additives used and incorporated into the gasoline contains one or more oxygen atoms, the gasoline will be considered as "without oxygenated compound" according to the definition given above. . By way of example, mention may be made of antioxidants chosen from hindered phenols (such as 2,6-di-t-butyl-4-methylphenol (BHT), 2,6-di-t-butyl- phenol and 2,4-di-methyl-6-t-butylphenol) usually used in aviation gasoline.

The invention also relates to the use of the composition defined above as an aircraft piston engine fuel.

EXAMPLES

The bases B1 (isopentane section), B2 (aviation alkylate) and B3 (aviation reformate), the compositions of which are given in Table 1 below, are used, the quantities indicated are expressed in percent by volume. Table 1 B1 isopentane 95 Paraffins in C4 and C5 99.2 olefins 0.8 B2 Isoparaffins in C8 ≤ 85 isooctane 45-55 2,2,3 trimethylpentane ≤ 5 Isoparaffins C4, C5, C6, C7 and C8 + ≤ 15 triptane 0.1 N-paraffins C4 to C7 0.8 aromatic - B3 aromatic 94.1 Benzene 0.06 Toluene 49 xylenes 29.2 Iso- and n-paraffins C4 to C8 + 4.6 Isoparaffins in C8 0.6

5 mixtures of the bases B1 to B3 described above are made and measure the MON, RON, PCI TV of the mixtures noted A to E.

The results are shown in Table 2 below. Table 2 AT B VS D E B1 (% by volume) 17 10 12 20 18 B2 (% by volume) 64 88 70 62 76 B3 (% by volume) 19 2 18 18 6 Isooctane (% by volume) 31.5 43.4 34.5 30.6 37.4 MON - ASTM D2700 92 92.9 92.6 92.1 92.4 RON 98.3 95.6 98.5 97.9 96.3 LHV (MJ / Kg) -ASTMD4529 43.47 44.41 43.53 43.56 44,17 TV (kPa) 46.3 43.8 38.9 48.1 48

Claims (8)

1. A lead-free aviation gasoline (AVGAZ) composition without any oxygenated compound comprising:

   from 14 to 22% by volume of isopentane (2-methyl-butane),

   from 30 to 40% by volume of isooctane (2,2,4-trimethyl-pentane),

   from 8 to 20% by volume of aromatics including 4 to 9% by volume of toluene,

   and containing not more than 1% of triptane (2,2,3-trimethyl-butane) and not more than 4% of 2,2,3-trimethyl-pentane.
2. The aviation gasoline composition according to claim 1, comprising from 20 to 22% by volume of isopentane,
   from 30 to 32% by volume of isooctane,
   from 15 to 18% by volume of aromatics, preferably comprising from 7 to 9% by volume of toluene.
3. The composition according to claim 1 or 2, the sulphur content of which measured according to the ASTM D1266 or ASTMD2622° standard is less than or equal to 500 ppm, preferably less than or equal to 100 ppm, or even less than or equal to 50 ppm, and still more advantageously less than or equal to 10 ppm.
4. The composition according to one of claims 1 to 3, further comprising one or more additives such as antioxidants, anti-icing agents, antistatic additives, corrosion inhibitors/lubricating power enhancer, agents enhancing cold properties, tracer additives, coloring agents, detergents and mixtures thereof.
5. A method for preparing a composition according to one of claims 1 to 45 comprising the mixing of

   • 10 to 20% by volume of at least one isopentane cut B1;

   • 62 to 88% by volume of at least one aviation alkylate base B2 essentially consisting of isoparaffins comprising 6 to 9 carbon atoms, preferably at least 90% by volume of isoparaffins comprising 6 to 9 carbon atoms;

   • 1 to 22% by volume of at least one base of the aviation reformate type B3 essentially consisting of alkylaromatics or aromatic.
6. The method according to claim 5, according to which in addition to bases B1 to B3, one or more other bases or cuts are added stemming from standard refining operations and/or synthetic hydrocarbons such as notably those obtained by oligomerization of olefins, by Fisher-Tropsch synthesis, by methods of the BTL (biomass to liquid), CTL (gas to liquid) and/or GTL (gas to liquid) type from materials of natural and/or synthetic origin, of animal and/or plant and/or fossil origin.
7. The method according to claim 5 or 6, according to which toluene and/or isooctane and/or isopentane are added to the mixture of bases B1, B2 and B3, and to the optional other bases.
8. Use of the composition according to one of claims 1 to 4 as a fuel for an aircraft piston engine.