(19) &   

(11) EP 1 650 289 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C10L 1/06 (2006.01) C10L 1/14 (2006.01) 04.04.2012 Bulletin 2012/14 C10L 1/18 (2006.01) C10L 1/22 (2006.01)

(21) Application number: 05256521.5

(22) Date of filing: 21.10.2005

(54) Aviation gasoline formulation Flugbenzinzusammensetzung Composition de carburant d’aviation

(84) Designated Contracting States: (56) References cited: DE FR GB GB-A- 911 491 US-A- 3 212 867 US-A1- 2002 026 744 US-A1- 2002 045 785 (30) Priority: 22.10.2004 BR 0404605 US-A1- 2003 183 554 US-B1- 6 258 134 US-B1- 6 451 075 (43) Date of publication of application: 26.04.2006 Bulletin 2006/17 • DATABASE WPI Section Ch, Week 199845 Derwent Publications Ltd., London, GB; Class (73) Proprietor: Petróleo Brasileiro S.A. - PETROBRAS E14, AN 1998-529537 XP002366367 & RO 113 365 Rio de Janeiro, RJ 20035-900 (BR) B (INST NATIONAL DE CERCETARI PEN) 30 June 1998 (1998-06-30) & RO 113 365 B1 (INSTITUTUL (72) Inventors: NATIONAL DE CERCETARI PENTRU RAFINARII • DE OLIVEIRA, Edimilson Jesus SI PETROCHIMIE, PLOI) 30 June 1998 Ingá, Niterói, RJ (BR) (1998-06-30) • ROCHA, Mauro Iurk • D. Atwood and J. Canizales: "DOT/FAA/AR- 04/25 Icaraí, Niterói, RJ (BR) Full scale engine knock tests of 30 unleaded, high-octane blends", September 2004 (2004-09), (74) Representative: Benson, John Everett US Department of Transportation; Federal J. A. Kemp & Co. Aviation Administration, Springfield, Virginia, 14 South Square USA * the whole document * Gray’s Inn • P MILLER: KITPLANES, June 2006 (2006-06), London WC1R 5JJ (GB) pages 29-35,

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 650 289 B1

Printed by Jouve, 75001 PARIS (FR) EP 1 650 289 B1

Description

FIELD OF THE INVENTION

5 [0001] The present invention relates to the field of the hydrocarbon compositions for use as fuels, more specifically, to unleaded aviation gasoline formulations for piston driven aircraft, which require high octane fuel.

BACKGROUND INFORMATION

10 [0002] In view of the increasing demand from environmental regulations, banning tetraethyl lead (TEL) from aviation gasoline (Avgas) formulations is a question of time. [0003] Thus, several companies and research groups are presently involved in projects aiming at providing fuel for- mulations having a performance similar to those using TEL. [0004] Such endeavor is not an easy task since such product should be endowed with special features among which 15 high octane rating, stability and high performance are among the most important items required for the new product. [0005] Alternative formulations described in the literature employ oxygenated compounds (ethyl tert-butyl ether - ETBE, ethyl alcohol) and aromatic amines, chiefly meta-toluidine (m-Tol) as components of the new fuels, all of them still being developed or tested and none of them being yet commercially available. [0006] Aviation gasoline fuels are mainly used in small passenger aircraft for leisure activities and also in small piston 20 driven helicopters. [0007] Because of the limited consuming market, aviation gasoline is produced in few refineries where the required stringent specifications are met without affecting too much the overall refinery budget. [0008] The development of a specific aviation gasoline fuel started in 1930. At that time the air sector of the US Army specified a combat gasoline fuel having a minimum octane number requirement of 87. This is believed to be the first 25 time the anti-knocking properties of an aviation gasoline fuel were defined in terms of octane number. In the beginning of Second World War fuels were similar to those of present class 100. [0009] Aviation gasoline attained its development peak during Second World War. In 1944, the US Army issued a specification for class 115/145. Such fuel had the highest anti- knocking evaluation among all commercial aviation gasoline and was used to obtain maximum response of high performance engines. 30 [0010] Useful streams for this kind of fuel should have a narrow distillation range and high octane numbers. C5 and C6 isoparaffin cuts - those being used in small concentrations due to their high volatility - or alkylates are generally sought for these formulations. [0011] Suitable additives are frequently the same as those used in jet engine fuels. However, the use of tetraethyl lead (TEL) is specific for aviation gasoline fuels. The use of this additive is specified in ASTM Method D 910 and the 35 amounts are a function of the fuel class. Maximum allowed levels are 0.14 g/L, 1.12 g/L, and 0.56 g/L, respectively for 80/87, 100/130, and 100/130LL classes. The only difference between the last two gasoline fuels is color and lead amount, with LL having the meaning of low lead. [0012] According to several fuel experts, for economic reasons the consumption of gasoline fuel for light aviation (100 LL gasoline fuel) can be suppressed in the next years. Without a substitute, many aircraft will no longer be able to fly. 40 The main reason for this concern is the quick decline in other TEL applications and a corresponding drop in the supply. [0013] A few years ago there were nearly 40-50 TEL suppliers while nowadays only two are left, one in the United Kingdom and another one in Russia. [0014] In spite of the research under course, at this moment there is no unleaded additive for Avgas. [0015] In spite of the rather modest contribution of Avgas for lead pollution, there is a huge concern of environmental 45 agencies for banning such lead source from the atmosphere. [0016] Lead-related additives constitute a further problem. [0017] Ethylene dibromide, another cleaning additive used with TEL in 100 LL gasoline fuel, is highly toxic and should also be banned since it is a chemical product leading to the greenhouse effect. Without this cleaning additive, lead can block the engine in a few hours. 50 [0018] Low consumption, soaring prices, added to the pressure from environmental agencies are parameters that tend to cause the end of leaded Avgas around 2005-2010. The same reasons make the basis for the research of a new product for an unleaded gasoline fuel. [0019] The patent literature teaches a few low lead or unleaded Avgas formulations. [0020] US patent 6,767,372 discloses an aviation gasoline (Avgas) fuel composition possessing a high motor octane 55 number containing reduced amounts of tetraethyl lead. The Avgas composition preferably comprises about 20 to about 80 vol % iso-octane, about 5 to about 18 vol % toluene, about 1 to about 20 vol % C4 to C5 paraffins, about 0 to about 1 mUgallon tetraethyl lead (TEL) and the balance light alkylate. The Avgas composition may be economically produced utilizing spare methyl tertiary butyl ether plant capacity to produce iso-octane as one component of the composition.

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[0021] US patent 6,451,075 relates to a particularly useful low lead aviation gasoline fuel blend that complies with all requirements of ASTM D 910 and includes 67.0 volume % isooctane, 18.0 volume % xylene, 12.0 volume % isopentane, 3.0 volume % isobutane and 0.47 mL/gal of tetraethyl lead. Another useful low lead aviation gasoline fuel blend which complies with all requirements of ASTM D 910 except for oxygenate content includes 60.0 volume % isooctane, 15.0 5 volume % xylene, 14.0 volume % methyl t- butyl ether, 8.0 volume % isopentane, 3.0 volume % isobutane and 0.2 mL/gal tetraethyl lead. The isooctane used in either case is a purified isooctane prepared either by fractionating a crude DIB (diisobutylene) material and hydrogenating the fractionated material or hydrogenating the crude DIB material and frac- tionating the hydrogenated material. [0022] US patents 6,258,134 and US 5,851,241 relate to aviation fuel compositions that contain a substantially positive 10 or synergistic combination of an alkyl tertiary butyl ether, an aromatic amine and, optionally, a manganese component. The base fuel containing the additive combination may be a wide boiling range alkylate. MON is at least 91, and is raised to at least 94 by the addition of the cited components. [0023] US patent 6,238,446 teaches unleaded aviation gasoline having heats of combustion and octane rating deemed necessary for use under actual service conditions that are formed from blends of specific proportions of aviation alkylate, 15 ether blending agent, a cyclopentadienyl manganese tricarbonyl and optionally other appropriate hydrocarbons falling in the gasoline boiling range. [0024] US patent 5,470,358 relates to an unleaded aviation gasoline fuel, containing additives such as aromatic amines substituted with C1-C10 alkyl or halogen, where the alkyl substituent cannot occupy the 2- or 6-position in the phenyl ring. According to this document, Avgas, due to stringent requirements in terms of octane rating and stability, is a blend 20 of isopentane, alkylate, toluene and TEL. A base fuel useful as Avgas without octane booster such as TEL has a MON rate of 90 to 93. MON, and not RON, is the accepted parameter for the Avgas octane and is measured using the ASTM Method 2700-92. The additive is used in amounts from 6 to 10 wt%, if necessary with the aid of a co-solvent. [0025] US Patent No. 3,212,867 relates to gasoline fuels containing a two-component additive consisting of a funda- mentally aromatic primary or secondary amine and a monocarboxylic acid or derivative thereof. These fuels can provide 25 an improvement in octane quality of a paraffinic hydrocarbon base fuel. [0026] US 2002/0045785 discloses an unleaded fuel composition having a MON of at least 98 and having a final boiling point of less than 170°C, namely an avgas suitable for use in piston-driven aircraft, which is formulated with at least 20% by volume of a branched alkane C7-C8, specifically triptane, and a C4-C10 saturated liquid aliphatic hydro- carbon. The avgas composition may also include octane boosters such as oxygenates and aromatic liquid hydrocarbons. 30 [0027] However, in spite of the present developments, the technique still needs an alkylate-based unleaded Avgas formulation, which preferably contains triptane (2,2,3-trimethyl butane) associated to toluidine and super-alkylate in suitable proportions to lead to an Avgas having suitable properties such Avgas formulation being described and claims in the present application.

35 SUMMARY OF THE INVENTION

[0028] Broadly, the invention relates to a gasoline formulation comprising, in percent volume, between 12 and 65.2 base alkylate, between 28 and 50 super-alkylate, between 20 and 30 toluene, between 3 and 10 of a toluidine isomer blend, between 0 and 5 ethyl alcohol, between 10 and 25 C5 cut and between 0 and 10 triptane, wherein the super- 40 alkylate is a distillation cut of the base alkylate containing between 75% and 78% by volume of isooctane. [0029] The gasoline formulation is suitably an aviation gasoline (Avgas) formulation, for example an unleaded Avgas formulation. The formulation is suitable for piston driven aircraft. [0030] Therefore, the invention provides an unleaded Avgas formulation useful for piston driven aircraft, as well as the use of a gasoline formulation as described above as an aviation gasoline formulation for piston driven aircraft. 45 [0031] The invention provides further an unleaded Avgas formulation where the octane boosters include super-alkylate, triptane and a blend of toluldine isomers. [0032] The invention also provides a method of preparing a gasoline formulation which method comprises blending, in percent volume, the following components: between 12 and 65.2 base alkylate, between 28 and 50 super-alkylate, between 20 and 30 toluene, between 3 and 10 of toluidine isomer blend, between 0 and 5 ethyl alcohol, between 10 50 and 25 C 5 cut and between 0 and 10 triptane, wherein the super-alkylate is a distillation cut of the base alkylate containing between 75% and 78% by volume isooctane and wherein the components of the gasoline formulation are blended in order from the most dense to the least dense except for the toluidine isomer blend which is the last component to be blended.

55 BRIEF DESCRIPTION OF THE DRAWINGS

[0033]

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FIGURE 1 attached is a graph illustrating the volume proportion of the evaporated from an alkylate feed to obtain super-alkylate. FIGURE 2 attached is a bar chart showing the MON and RON values for several unleaded Avgas formulations. C is for Control, a state-of-the-art formulation. 5 DETAILED DESCRIPTION OF THE PREFERRED MODES

[0034] Therefore, in a preferred embodiment the present invention deals with an unleaded Avgas formulation for piston driven aircraft. 10 [0035] By volume, the formulation includes between 0 and 65.2% base alkylate, between 0 and 50% super-alkylate, between 0 and 25% toluene, between 2 and 10% of a toluidine isomer blend, between 0 and 5% ethyl alcohol, between 0 and 25% C5 cut and between 0 and 10% triptane. [0036] Volume proportions of some preferred formulations are for example as in Table 1 below.

15 TABLE 1 COMPONENTS % vol/vol Alkylate 12-18 Super Alkylate 28-42 20 Toluene 20-30 Toluidines 3-5 Ethyl alcohol 0-5

25 C5 stream 10-20 Triptane 0-10

[0037] Base alkylate is a product obtained by the alkylation process of the petroleum industry whereby a stream, 30 generally formed by isobutane and cis/ trans 2-butene reacts under conditions of acidic catalysis, to yield poly branched hydrocarbons in the gasoline boiling range (alkylate) the major fractions of which contains 8 carbon atoms. Gasoline fuel obtained by this process has an excellent quality in terms of octane number and oxidation stability besides complying with several environmental requirements that are being progressively implemented aiming at modifying gasoline com- position so that it is less harmful to man and environment. 35 [0038] Super-alkylate means, in the present invention, a distillation cut of the base alkylate containing between 75% and 78% by volume of isooctane. Such cut works as an octane booster for the Avgas formulation. The superalkylate is a stream obtained by the fractioning of the base alkylate. The range of interest is between 95°C and 105°C since the boiling point of isooctane is 99.4°C. The way to obtain super alkylate is depicted in Figure 1. [0039] Other physical properties of alkylate and super alkylate can be found in Table 2 below. 40 TABLE 2 Stream Feature Unit Method Alkylate Superalkylate 45 RON - ASTM D-2699 94.4 100.6 MON - ASTM D-2700 93.5 96.5- Density@ 20/4°C - ASTM D-4052 0.6919 0.7008

50 [0040] Preferably the gasoline formulation has a motor octane number of not less than 93.5, more preferably of not less than 94.4, for example about 102.4. [0041] According to the invention, useful toluidines are a blend of toluidine isomers in any amount. Although the literature mentions chiefly m- toluidine as octane booster, the Applicant has experimentally determined that isomer blends

55 can be used, this representing an economic advantage. [0042] Triptane is an octane booster, 2,2,3-trimethyl butane. [0043] Toluene is commercial toluene. [0044] C5 is a refinery cut having boiling point between 35.5°C and 48°C.

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[0045] As regards the method to prepare the formulations according to the invention, the order of blending the com- ponents should be from the denser to the less dense, except in the case of meta-toluidine, which in spite of being the denser product is the latest to be mixed to the other streams. This is due to homogenization problems experienced by meta-toluidine. 5 [0046] The bar chart of Figure 2 illustrates the formulations used in the Examples listed in Tables 3 and 4 below. In this chart, the symbol C in the abscissa means Control. [0047] The invention will now be illustrated by the following non- limiting Examples 3, 4, 8 and 11 according to Tables 3 and 4 below, formulations 2, 5-7, 9, 10, 12-15 not being according to the invention.

10 TABLE 3 Super Triptane Alkylate Toluene Toluidines Ethyl alcohol C5 Stream Formulation Alkylate % vol/vol 15 Control 65.0 0.0 15.0 0.0 0.0 20.0 0.0 2 65.2 0.0 15.0 3.0 0.0 16.8 0.0 3 17.3 33.1 25.0 3.0 5.0 16.6 0.0 4 17.0 40.0 23.5 3.0 0.0 16.5 0.0 20 5 0.0 50.0 25.0 4.0 0.0 21.0 0.0 6 40.0 50.0 0.0 10.0 0.0 0.0 0.0 7 8.0 47.0 20.0 3.0 0.0 22.0 0.0 25 8 15.0 35.0 25.0 4.0 0.0 21.0 0.0 9 16.0 50.0 15.0 4.0 0.0 15.0 0.0 10 24.2 50.0 10.0 6.0 0.0 9.8 0.0

30 11 15.0 35.5 25.0 3.5 0.0 21.0 0.0 12 16.0 40.0 15.0 4.0 0.0 25.0 0.0 13 0.0 45.0 25.0 4.0 0.0 21.0 5.0 14 0.0 40.0 25.0 4.0 0.0 21.0 10.0 35 15 10.0 35.0 23.0 4.0 0.0 21.0 7.0

TABLE 4 40 Formulation MON RON Control 89.7 94.6 295.4102

45 395.2100 4 96.5 103.6 596.8104 6 102.4 107 50 7 94.4 102.4 896105 997.7105

55 10 101.4 108 11 97.6 105 12 97.4 104

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(continued) Formulation MON RON 13 98 106 5 14 101 108.8 15 99.5 107

[0048] As illustrated by the bar chart of Figure 2 and Tables 3 and 4 above, it should be pointed out that: 10 • As expected, the addition of toluidines (isomer blend) neatly increases MON values for a certain formulation; • Formulations containing triptane and super alkylate attain high MON values even for reduced amounts of toluidines; • The presence of ethyl alcohol in a formulation does not seem to have any effect at least in the amount used. The use of ethyl alcohol can be considered in alternative/optional formulations since this compound is attractive under 15 environmental considerations besides being an octane booster. However employing ethyl alcohol in a formulation designed for an aircraft should be cautiously thought of since such fuel can show phase separation, water absorption and freeze at the altitude level of aircraft fly.

[0049] In conclusion, the proposed formulations state that it is possible to obtain high MON levels for an unleaded 20 Avgas, the booster effect being obtained by including specified amounts of a high isooctane cut such as super- alkylate, besides triptane and relatively reduced contents of toluidine isomer blends.

Claims 25 1. A gasoline formulation comprising, in percent volume, between 12 and 65.2 base alkylate, between 28 and 50 super- alkylate, between 20 and 30 toluene, between 3 and 10 of a toluidine isomer blend, between 0 and 5 ethyl alcohol, between 10 and 25 C 5 cut and between 0 and 10 triptane, wherein the super- alkylate is a distillation cut of the base alkylate containing between 75% and 78% by volume of isooctane. 30 2. A gasoline formulation according to claim 1, wherein it comprises, in percent volume, from 12 to 18 alkylate, 28 to 42 superalkylate, 20 to 30 toluene, 3 to 5 toluidine isomer blend, 0 to 5 ethyl alcohol, 10 to 20 of C5 stream, and 0 to 10 triptane.

35 3. A gasoline formulation according to claim 1 or claim 2, wherein the base alkylate is obtainable by alkylating an isobutane and a cis/trans 2-butene stream under acidic catalysis conditions, to form poly branched hydrocarbons in the gasoline boiling point range with a major fraction having 8 carbon atoms.

4. A gasoline formulation according to claim 1, wherein the formulation has a motor octane number (MON) of not less 40 than 94.4.

5. A gasoline formulation according to claim 1, wherein the formulation has a motor octane number (MON) of 102.4.

6. A gasoline formulation according to any one of the preceding claims which is an aviation gasoline (Avgas) formulation 45 for piston driven aircraft.

7. A method of preparing a gasoline formulation which method comprises blending, in percent volume, the following components: between 12 and 65.2 base alkylate, between 28 and 50 super-alkylate, between 20 and 30 toluene, between 3 and 10 of toluidine isomer blend, between 0 and 5 ° ethyl alcohol, between 10 and 25 C 5 cut and between 50 0 and 10 triptane, wherein the super-alkylate is a distillation cut of the base alkylate containing between 75% and 78% by volume isooctane and wherein the components of the gasoline formulation are blended in order from the most dense to the least dense except for the toluidine isomer blend which is the last component to be blended.

8. A method according to claim 7 wherein the components of the gasoline formulation are as defined in claim 2 or 3. 55 9. Use of a gasoline formulation according to any one of claims 1 to 5 or produced according to the method of claim 7 or claim 8 as an aviation gasoline (Avgas) formulation for piston driven aircraft.

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Patentansprüche

1. Benzinzusammensetzung, umfassend, in Volumenprozent, zwischen 12 und 65,2 Alkylat-Basisbenzin, zwischen 28 und 50 Super- Alkylat, zwischen 20 und 30 Toluol, zwischen 3 und 10 eines Toluidin-Isomerengemischs, zwischen 5 0 und 5 Ethylalkohol, zwischen 10 und 25 C5-Schnitt und zwischen 0 und 10 Triptan, wobei das Super-Alkylat ein Destillationsschnitt des Alkylat-Basisbenzins ist, der zwischen 75 %- und 78 %- Volumenanteilen an Isooktan enthält.

2. Benzinzusammensetzung nach Anspruch 1, wobei diese umfasst, in Volumenprozent, von 12 bis 18 Alkylat, 28 bis 42 Super-Alkylat, 20 bis 30 Toluol, 3 bis 5 Toluidin- Isomerengemisch, 0 bis 5 Ethylalkohol, 10 bis 20 C 5-Strom und 10 0 bis 10 Triptan.

3. Benzinzusammensetzung nach Anspruch 1 oder Anspruch 2, wobei das Alkylat-Basisbenzin durch Alkylieren eines Isobutan- und eines cis/trans-2-Buten-Stroms unter sauren Katalysebedingungen erhaltbar ist, um mehrfach ver- zweigte Kohlenwasserstoffe im Siedebereich von Benzin zu bilden, von denen eine größere Fraktion 8 Kohlen- 15 stoffatome aufweist.

4. Benzinzusammensetzung nach Anspruch 1, wobei die Zusammensetzung eine Motor-Oktanzahl (MON) von nicht weniger als 94,4 aufweist.

20 5. Benzinzusammensetzung nach Anspruch 1, wobei die Zusammensetzung eine Motor- Oktanzahl (MON) von 102,4 aufweist.

6. Benzinzusammensetzung nach jedem der vorangehenden Ansprüche, welche eine Flugbenzin-(Avgas)-Zusam- mensetzung für kolbenbetriebene Flugzeuge ist. 25 7. Verfahren zur Herstellung einer Benzinzusammensetzung, welches Verfahren das Mischen, in Prozentvolumen, der folgenden Komponenten umfasst:

zwischen 12 und 65,2 Alkylat-Basisbenzin, zwischen 28 und 50 Super-Alkylat, zwischen 20 und 30 Toluol, 30 zwischen 3 und 10 eines Toluidin-Isomerengemischs, zwischen 0 und 5 Ethylalkohol, zwischen 10 und 25 C5-Schnitt und zwischen 0 und 10 Triptan, wobei das Super-Alkylat ein Destillationsschnitt des Alkylat-Basis- benzins ist, der zwischen 75 %- und 78 %-Volumenanteilen an Isooktan enthält und wobei die Komponenten der Benzinzusammensetzung in der Reihenfolge von der dichtesten zu der am wenigsten dichten gemischt werden, mit Ausnahme des Toluidin- Isomerengemischs, welches die zuletzt beizumischende Komponente ist. 35 8. Verfahren nach Anspruch 7, wobei die Komponenten der Benzinzusammensetzung wie in Anspruch 2 oder 3 definiert sind.

9. Verwendung einer Benzinzusammensetzung nach jedem der Ansprüche 1 bis 5 oder wie gemäß des Verfahrens 40 nach Anspruch 7 oder Anspruch 8 hergestellt, als eine Flugbenzin-(Avgas)-Zusammensetzung für kolbenbetriebene Flugzeuge.

Revendications 45 1. Formulation d’essence comprenant, en pourcentage en volume, entre 12 et 65,2 d’un alkylat de base, entre 28 et 50 d’un super-alkylat, entre 20 et 30 de toluène, entre 3 et 10 d’un mélange d’isomères de toluidine, entre 0 et 5 d’alcool éthylique, entre 10 et 25 d’une fraction en C 5 et entre 0 et 10 de triptane, dans laquelle le super- alkylat est une fraction de distillation de l’alkylat de base contenant entre 75 % et 78 % en volume d’iso-octane. 50 2. Formulation d’essence selon la revendication 1, qui comprend, en pourcentage en volume, de 12 à 18 d’alkylat, de 28 à 42 de super-alkylat, de 20 à 30 de toluène, de 3 à 5 de mélange d’isomères de toluidine, de 0 à 5 d’alcool éthylique, de 10 à 20 d’un courant en C5 et de 0 à 10 de triptane.

55 3. Formulation d’essence selon la revendication 1 ou la revendication 2, dans laquelle l’alkylat de base peut être obtenu par alkylation d’un isobutane et d’un courant de 2-butène cis/trans dans des conditions de catalyse acide, pour former des hydrocarbures à plusieurs ramifications dans la limite des points d’ébullition de l’essence, une fraction majeure comportant 8 atomes de carbone.

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4. Formulation d’essence selon la revendication 1, dans laquelle la formulation a un indice d’octane moteur (MON) non inférieur à 94, 4.

5. Formulation d’essence selon la revendication 1, dans laquelle la formulation a un indice d’octane moteur (MON) de 5 102,4.

6. Formulation d’essence selon l’une quelconque des revendications précédentes, qui est une formulation d’essence d’aviation (Avgas) pour avions à moteurs à pistons.

10 7. Procédé de préparation d’une formulation d’essence, qui comprend le mélange, en pourcentage en volume, des composants suivants : entre 12 et 65,2 d’un alkylat de base, entre 28 et 50 d’un super-alkylat, entre 20 et 30 de toluène, entre 3 et 10 d’un mélange d’isomères de toluidine, entre 0 et 5 d’alcool éthylique, entre 10 et 25 d’une fraction en C5 et entre 0 et 10 de triptane, dans lequel le super-alkylat est une fraction de distillation de l’alkylat de base contenant entre 75 % et 78 % en volume d’iso-octane et dans lequel les composants de la formulation d’essence 15 sont mélangés dans l’ordre du plus dense au moins dense, hormis pour le mélange d’isomères de toluidine qui est le dernier composant à être mélangé.

8. Procédé selon la revendication 7, dans lequel les composants de la formulation d’essence sont tels que définis dans la revendication 2 ou 3. 20 9. Utilisation d’une formulation d’essence selon l’une quelconque des revendications 1 à 5 ou produite selon le procédé de la revendication 7 ou de la revendication 8, comme formulation d’essence d’aviation (Avgas) pour avions à moteurs à pistons.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 6767372 B [0020] • US 6238446 B [0023] • US 6451075 B [0021] • US 5470358 A [0024] • US 6258134 B [0022] • US 3212867 A [0025] • US 5851241 A [0022] • US 20020045785 A [0026]

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