Classifications

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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/04—Liquid carbonaceous fuels essentially based on blends of hydrocarbons
  • C10L1/06—Liquid carbonaceous fuels essentially based on blends of hydrocarbons for spark ignition
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/185—Ethers; Acetals; Ketals; Aldehydes; Ketones
  • C10L1/1852—Ethers; Acetals; Ketals; Orthoesters
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L10/00—Use of additives to fuels or fires for particular purposes
  • C10L10/10—Use of additives to fuels or fires for particular purposes for improving the octane number
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/16—Hydrocarbons
  • C10L1/1608—Well defined compounds, e.g. hexane, benzene
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/16—Hydrocarbons
  • C10L1/1616—Hydrocarbons fractions, e.g. lubricants, solvents, naphta, bitumen, tars, terpentine
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/182—Organic compounds containing oxygen containing hydroxy groups; Salts thereof
  • C10L1/1822—Organic compounds containing oxygen containing hydroxy groups; Salts thereof hydroxy group directly attached to (cyclo)aliphatic carbon atoms
  • C10L1/1824—Organic compounds containing oxygen containing hydroxy groups; Salts thereof hydroxy group directly attached to (cyclo)aliphatic carbon atoms mono-hydroxy
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/19—Esters ester radical containing compounds; ester ethers; carbonic acid esters
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/22—Organic compounds containing nitrogen
  • C10L1/222—Organic compounds containing nitrogen containing at least one carbon-to-nitrogen single bond
  • C10L1/223—Organic compounds containing nitrogen containing at least one carbon-to-nitrogen single bond having at least one amino group bound to an aromatic carbon atom
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2200/00—Components of fuel compositions
  • C10L2200/04—Organic compounds
  • C10L2200/0407—Specifically defined hydrocarbon fractions as obtained from, e.g. a distillation column
  • C10L2200/0415—Light distillates, e.g. LPG, naphtha
  • C10L2200/0423—Gasoline
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2270/00—Specifically adapted fuels
  • C10L2270/02—Specifically adapted fuels for internal combustion engines
  • C10L2270/023—Specifically adapted fuels for internal combustion engines for gasoline engines
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2270/00—Specifically adapted fuels
  • C10L2270/04—Specifically adapted fuels for turbines, planes, power generation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L2300/00—Mixture of two or more additives covered by the same group of C10L1/00 - C10L1/308
  • C10L2300/40—Mixture of four or more components

Definitions

• the present invention relates to unleaded aviation gasoline fuel, in particular to unleaded aviation gasoline fuel having improved octane properties.
• Avgas aviation gasoline
• mogas motor gasoline
• avgas contains tetraethyl lead (TEL), a non- biodegradable toxic substance used to prevent engine knocking (detonation).
• TEL tetraethyl lead
• Aviation gasoline fuels currently contain the additive tetraethyl lead (TEL), in amounts up to 0.53 mL/L or 0.56 g/L which is the limit allowed by the most widely used aviation gasoline specification 100 Low Lead (100LL).
• TEL tetraethyl lead
• 100LL Low Lead
• the lead is required to meet the high octane demands of aviation piston engines: the 100LL specification ASTM D910 demands a minimum motor octane number (MON) of 99.6, in contrast to the EN 228 specification for European motor gasoline which stipulates a minimum MON of 85 or United States motor gasoline which require unleaded fuel minimum octane rating (R+M)/2 of 87.
• MON motor octane number
• Aviation fuel is a product which has been developed with care and subjected to strict regulations for aeronautical application. Thus aviation fuels must satisfy precise physico-chemical characteristics, defined by international specifications such as ASTM D910 specified by Federal Aviation Administration (FAA). Automotive gasoline is not a fully viable replacement for avgas in many aircraft, because many high-performance and/or turbocharged airplane engines require 100 octane fuel (MON of 99.6) and modifications are necessary in order to use lower-octane fuel. Automotive gasoline can vaporize in fuel lines causing a vapor lock (a bubble in the line) or fuel pump cavitation, starving the engine of fuel.
• MON octane fuel
• Vapor lock typically occurs in fuel systems where a mechanically-driven fuel pump mounted on the engine draws fuel from a tank mounted lower than the pump.
• the reduced pressure in the line can cause the more volatile components in automotive gasoline to flash into vapor, forming bubbles in the fuel line and interrupting fuel flow.
• the ASTM D910 specification does not include all gasoline satisfactory for reciprocating aviation engines, but rather, defines the following specific types of aviation gasoline for civil use: Grade 80; Grade 91;
• Grade 100; and Grade 100LL are considered High Octane Aviation Gasoline to meet the requirement of modern demanding aviation engines.
• D910 specification for Avgas has the following requirements: density; distillation (initial and final boiling points, fuel evaporated, evaporated temperatures T10, T40, T90, T10+T50); recovery, residue, and loss volume; vapor pressure; freezing point; sulfur content; net heat of combustion; copper strip corrosion; oxidation stability (potential gum and lead precipitate); volume change during water reaction; electrical conductivity; and other properties.
• Avgas fuel is typically tested for its properties using ASTM tests: Motor Octane Number: ASTM D2700 Aviation Lean Rating: ASTM D2700 Performance Number (Super-Charge): ASTM D909 Tetraethyl Lead Content: ASTM D5059 or ASTM D3341 Color: ASTM D2392
• US Patent No. 9120991 discloses unleaded aviation fuel compositions comprising toluene, toluidine, alkylate or alkylate blend, branched acetate and isopentane.
• US Patent No. 9388356 discloses unleaded aviation fuel compositions comprising toluene, aniline, alkylate or alkylate blend, branched chain alcohol and isopentane.
• US Patent No. 9388357 discloses unleaded aviation fuel compositions comprising toluene, aromatic amine component comprising toluidine, alkylate or alkylate blend and isopentane.
• US Patent No. 9388358 discloses unleaded aviation fuel compositions comprising toluene, aniline, alkylate or alkylate blend, diethyl carbonate, and isopentane.
• US Patent No. 9388359 discloses unleaded aviation fuel compositions comprising toluene, toluidine, alkylate or alkylate blend, diethyl carbonate and isopentane.
• US Patent No. 9035114 discloses unleaded aviation fuel compositions comprising toluene, aniline, alkylate or alkylate blend, branched alkyl acetate and isopentane.
• US Patent No. 9127225 discloses unleaded aviation fuel compositions comprising toluene, aniline, alkylate or alkylate blend, C4-C5 alcohol, and isopentane.
• an unleaded aviation fuel composition having a MON of at least 99.6, sulfur content of less than 0.05 wt%, CHN content of at least 97.2 wt%, less than 2.8 wt% of oxygen content, a T10 of at most 75°C, T40 of at least 75° C, a T50 of at most 105° C, a T90 of at most 135°C, a final boiling point of less than 190°C, an adjusted heat of combustion of at least 43.5 MJ/kg, a vapor pressure in the range of 38 to 49 kPa, comprising from 20 vol.% to 35 vol.% of toluene having a MON of at least 107; from 2 vol.% to 10 vol.% of aniline; from above 30 vol% to 55 vol% of at least one alkylate or alkyate blend having an initial boiling range of from 32°C to 60°C and a final boiling range of from 105°C to 140°C, having T40 of less than 99°
• the fuel composition of the present invention has improved octane properties.
• Figure 1 is a graphical representation of the data set out in Tables 6-8.
• the unleaded aviation fuel composition of the present invention can be produced by a blend comprising from about 20 vol% to about 35 vol% of high MON toluene, from about 2 vol% to about 10 vol% of aniline, from about 30 vol% to about 55 vol% of at least one alkylate cut or alkylate blend that have certain composition and properties, at least 8 vol% of isopentane, from 0.1 vol% to 10 vol% of a straight chain alkyl acetate and from 0.1 vol% to 10 vol% of a branched chain alcohol.
• the volume ratio of straight chain alkyl actetate to branched chain alcohol is in the range of 3:1 to 1:3.
• the high octane unleaded aviation fuel of the invention has a MON of greater than 99.6.
• the unleaded aviation fuel composition contains less than 1 vol%, preferably less than 0.5 vol% of C8 aromatics. It has been found that C8 aromatics such as xylene may have materials compatibility issues, particularly in older aircraft. Further it has been found that unleaded aviation fuel containing C8 aromatics tend to have difficulties meeting the temperature profile (ASTM D86) of D910 specification.
• the unleaded aviation fuel contains no noncyclic ethers. In another embodiment, the unleaded aviation fuel contains no alcohol boiling less than 80°C. Further, the unleaded aviation fuel composition has a benzene content between 0%v and 5%v, preferably less than l%v.
• the volume change of the unleaded aviation fuel tested for water reaction is within +/- 2mL as defined in ASTM D1094.
• the high octane unleaded fuel will not contain lead and preferably not contain any other metallic octane boosting lead equivalents.
• the term "unleaded” is understood to contain less than O.Olg/L of lead.
• the high octane unleaded aviation fuel will have a sulfur content of less than 0.05 wt%. In some embodiments, it is preferred to have ash content of less than 0.0132g/L (0.05 g/gallon) (ASTM D-482).
• the NHC should be close to or above 43.5mJ/kg.
• the Net Heat of Combustion value is based on a current low density aviation fuel and does not accurately measure the flight range for higher density aviation fuel. It has been found that for unleaded aviation gasolines that exhibit high densities, the heat of combustion may be adjusted for the higher density of the fuel to more accurately predict the flight range of an aircraft.
• ASTM D910 There are currently three approved ASTM test methods for the determination of the heat of combustion within the ASTM D910 specification. Only the ASTM D4809 method results in an actual determination of this value through combusting the fuel. The other methods (ASTM D4529 and ASTM D3338) are calculations using values from other physical properties. These methods have all been deemed equivalent within the ASTM D910 specification.
• HOC* (HOCv/density)+(% range increase/% payload increase +1)
• HOC* is the adjusted Heat of Combustion (MJ/kg)
• HOCv is the volumetric energy density (MJ/L) obtained from actual Heat of Combustion measurement
• density is the fuel density (g/L)
• % range increase is the percentage increase in aircraft range compared to 100 LL(HOCLL) calculated using HOCv and HOCLL for a fixed fuel volume
• % payload increase is the corresponding percentage increase in payload capacity due to the mass of the fuel.
• the adjusted heat of combustion will be at least 43.5MJ/kg, and have a vapor pressure in the range of 38 to 49 kPa.
• the high octane unleaded fuel composition will further have a freezing point of -58°C or less. Unlike for automobile fuels, for aviation fuel, due to the altitude while the plane is in flight, it is important that the fuel does not cause freezing issues in the air.
• the final boiling point of the high octane unleaded fuel composition should be less than 190°C, preferably at most 180°C measured with greater than 98.5% recovery as measured using ASTM D-86. If the recovery level is low, the final boiling point may not be effectively measured for the composition (i.e., higher boiling residual still remaining rather than being measured).
• the high octane unleaded aviation fuel composition of the invention have a Carbon, Hydrogen, and Nitrogen content (CHN content) of at least 98 wt%, preferably 99 wt%, (and less than 2wt%, preferably lwt% or less of oxygen-content.
• the unleaded aviation fuel composition of the present invention has an aromatics content measured according to ASTM D5134 of greater than 15 vol% to about 35 vol%, preferably in the range of 20 vol% to about 35 vol%, more preferably in the range from 20 vol% to 30 vol%, by weight of the total unleaded aviation fuel composition.
• the high octane unleaded aviation fuel of the invention not only meets the MON value for 100 octane aviation fuel, but also meets the vapor pressure, adjusted heat of combustion, and freezing point.
• MON it is important to meet the vapor pressure, temperature profile, and minimum adjusted heat of combustion for aircraft engine start up and smooth operation of the plane at higher altitude.
• the potential gum value is less than 6mg/100mL.
• the high octane unleaded aviation fuel has T10 of at most 80°C, a T40 of at least 75°C, a T50 of at most 105°C, a T90 of at most 135°C and a final boiling point of less than 190°C.
• the unleaded aviation fuel composition of the present invention comprising a certain blend of components in certain amounts serves to address this problem.
• Toluene occurs naturally at low levels in crude oil and is usually produced in the processes of making gasoline via a catalytic reformer, in an ethylene cracker or making coke from coal. Final separation, either via distillation or solvent extraction, takes place in one of the many available processes for extraction of the BTX aromatics (benzene, toluene and xylene isomers).
• the toluene used in the invention must be a grade of toluene that have a MON of at least 107 and containing less than lvol% of C8 aromatics. Further, the toluene component preferably has a benzene content between 0%v and 5%v, preferably less than l%v.
• an aviation reformate is generally a hydrocarbon cut containing at least 70% by weight, ideally at least 85% by weight of toluene, and it also contains C8 aromatics (15 to 50% by weight ethylbenzene, xylenes) and C9 aromatics (5 to 25% by weight propyl benzene, methyl benzenes and trimethylbenzenes).
• Such reformate has a typical MON value in the range of 102- 106, and it has been found not suitable for use in the present invention.
• Toluene is preferably present in the blend in an amount from about 20%v, preferably at least about 25%v, to at most about 40%v, preferably to at most about 35%v, more preferably to at most about 30%v, based on the unleaded aviation fuel composition.
• Aniline (C6H5NH2) is mainly produced in industry in two steps from benzene.
• benzene is nitrated using a concentrated mixture of nitric acid and sulfuric acid at 50 to 60°C, which gives nitrobenzene.
• the nitrobenzene is hydrogenated, typically at 200- 300°C in presence of various metal catalysts.
• aniline is also prepared from phenol and ammonia, the phenol being derived from the cumene process.
• aniline oil for blue which is pure aniline
• aniline oil for red a mixture of equimolecular quantities of aniline and ortho- and para-toluidines
• aniline oil for safranine which contains aniline and ortho-toluidine, and is obtained from the distillate (echappes) of the fuchsine fusion.
• Pure aniline, otherwise known as aniline oil for blue is desired for high octane unleaded avgas.
• Aniline is preferably present in the blend in an amount from about 2%v, preferably at least about 3%v, most preferably at least about 4%v to at most about 10%v, preferably to at most about 7%v, more preferably to at most about 6%v, based on the unleaded aviation fuel composition.
• alkylate typically refers to branched-chain paraffin.
• the branched-chain paraffin typically is derived from the reaction of isoparaffin with olefin.
• Various grades of branched chain isoparaffins and mixtures are available. The grade is identified by the range of the number of carbon atoms per molecule, the average molecular weight of the molecules, and the boiling point range of the alkylate. It has been found that a certain cut of alkylate stream and its blend with isoparaffins such as isooctane is desirable to obtain or provide the high octane unleaded aviation fuel of the invention.
• These alkylate or alkylate blend can be obtained by distilling or taking a cut of standard alkylates available in the industry.
• the alkylate or alkyate blend have an initial boiling range of from about 32°C to about 60°C and a final boiling range of from about 105°C to about 140°C, preferably to about 135°C, more preferably to about 130°C, most preferably to about 125°C, having T40 of less than 99°C, preferably at most 98C, T50 of less than 100°C, T90 of less than 110°C, preferably at most 108°C, the alkylate or alkylate blend comprising isoparaffins from 4 to 9 carbon atoms, about 3-20 vol% of C5 isoparaffins, based on the alkylate or alkylate blend, about 3-15 vol% of C7 isoparaffins, based on the alkylate or alkylate blend, and about 60-90 vol% of C8 isoparaffins, based on the alkylate or alkylate blend, and less than 1 vol% of C10+, preferably less than
• Alkylate or alkylate blend is preferably present in the unleaded aviation fuel composition in an amount from about 30%v, preferably at least about 32%v, most preferably at least about 35%v to at most about 55%v, preferably to at most about 49%v, more preferably to at most about 47%v, based on the unleaded aviation fuel composition.
• Isopentane is present in an amount of at least 8 vol% in an amount sufficient to reach a vapor pressure in the range of 38 to 49 kPa.
• the alkylate or alkylate blend also contains C5 isoparaffins so this amount will typically vary between 5 vol% and 25 vol% depending on the C5 content of the alkylate or alkylate blend.
• Isopentane should be present in an amount to reach a vapor pressure in the range of 38 to 49 kPa to meet aviation standard.
• the total isopentane content in the unleaded aviation fuel composition is typically in the range of 10 vol% to 26 vol%, preferably in the range of 12% to 18% by volume, based on the unleaded aviation fuel composition.
• the unleaded aviation fuel composition contains a straight chain alkyl acetate having a straight chain alkyl group having 4 to 8 carbon atoms as a co-solvent.
• Straight chain alkyl acetates having from 4 to 8 carbon atoms includes n-butyl acetate, n-pentyl acetate, n-hexyl acetate, n-heptyl acetate and n-octyl acetate.
• the straight chain alkyl group has from 4 to 6 carbon atoms, more preferably 4 or 5 carbon atoms, and especially 4 carbon atoms. It has been found that the larger the co-solvent molecule, the higher the density of the fuel, which may lead to soot issues associated with the use of higher density fuels in piston engines.
• the co-solvent for use herein is n-butyl acetate.
• the unleaded aviation fuels containing aromatic amines tend to be significantly more polar in nature than traditional aviation gasoline base fuels. As a result, they have poor solubility in the fuels at low temperatures, which can dramatically increase the freeze points of the fuels.
• an aviation gasoline base fuel comprising 10% v/v isopentane, 70% v/v light alkylate and 20% v/v toluene.
• This blend has a MON of around 90 to 93 and a freeze point (ASTM D2386) of less than -76°C.
• the addition of 6% w/w (approximately 4% v/v) of the aromatic amine aniline increases the MON to 96.4.
• the straight chain alkyl acetate is present in an amount from 0.1 vol%, to 10 vol%, preferably from 1 vol% to 8 vol%, more preferably from 3 vol% to 6 vol%, even more preferably from 4 vol% to 6 vol%, based on the unleaded aviation fuel composition.
• the straight chain alkyl acetate is useful in combination with the branched alkyl alcohol for providing improved octane characteristics.
• the volume ratio of the straight chain alkyl actetate to branched chain alkyl alcohol is in the range of 2:1 to 1:2, most preferably at a ratio of 1:1.
• the water reaction volume change is within +/- 2ml for aviation fuel.
• Water reaction volume change is large for ethanol that makes ethanol not suitable for aviation gasoline.
• the unleaded aviation fuel composition contains a branched chain alcohol having from 4 to 8 carbon atoms, preferably from 4 to 6 carbon atoms, as an additional co solvent, provided that the branched chain does not include t-butyl groups.
• Suitable branched chain alcohols as an additional co-solvent may be, for example, iso butyl alcohol, iso-pentyl alcohol, iso-hexyl alcohol, iso-heptyl alcohol, iso-octyl alcohol, and mixtures thereof.
• the branched chain alcohol is present in an amount from 0.1 vol%, to 10 vol%, preferably from 2 vol% to 8vol%, more preferably from 3 vol% to 6 vol%, even more preferably from 4 vol% to 6 vol%, based on the unleaded aviation fuel composition.
• a preferred branched chain alcohol for use herein is isobutyl alcohol (IBA).
• the unleaded aviation fuel composition comprises 4 vol% of branched chain alcohol and 4 vol% of straight chain acetate.
• the blending can be in any order as long as they are mixed sufficiently. It is preferable to blend the toluene, and alkylate blend together, followed by the isopentane, isobutane, and then the straight chain alkyl acetate, the branched chain alcohol and the aniline (in that order) and to mix the blend for about 2 hours. This order of addition helps to prevent the aniline dropping out of solution.
• the unleaded aviation fuel according to the invention may contain one or more additives which a person skilled in the art may choose to add from standard additives used in aviation fuel.
• additives such as antioxidants, anti-icing agents, antistatic additives, corrosion inhibitors, dyes and their mixtures.
• a method for operating an aircraft engine, and/or an aircraft which is driven by such an engine involves introducing into a combustion region of the engine and the high octane unleaded aviation gasoline fuel formulation described herein.
• the aircraft engine is suitably a spark ignition piston-driven engine.
• a piston-driven aircraft engine may for example be of the inline, rotary, V-type, radial or horizontally-opposed type.
• the unleaded aviation gasoline fuel formulation described herein provides improvements in octane properties.
• an unleaded aviation fuel composition having a MON of at least 99.6, sulfur content of less than 0.05 wt%, CHN content of at least 97.2 wt%, less than 2.8 wt% of oxygen content, a T10 of at most 75°C, T40 of at least 75° C, a T50 of at most 105° C, a T90 of at most 135°C, a final boiling point of less than 190°C, an adjusted heat of combustion of at least 43.5 MJ/kg, a vapor pressure in the range of 38 to 49 kPa, comprising from 20 vol.% to 35 vol.% of toluene having a MON of at least 107; from 2 vol.% to 10 vol.% of aniline; from above 30 vol% to 55 vol% of at least one alkylate or alkyate blend having an initial boiling range of from
• the term 'improved octane properties' means that the unleaded aviation fuel composition has an increased MON value.
• MON is used for measuring the antiknock performance of spark-ignition engine fuels. It is utilized to determine, by correlation equation, the Aviation method octane number or performance number. The higher the octane number, the more compression the fuel can withstand before detonating. Fuels with higher octane allow higher performance of gasoline engines.
• the term 'improved octane properties' embraces any degree of improvement in octane properties.
• the improvement in octane properties may be of the order of 0.5% or more, preferably 1% or more, more preferably 5% or more, and especially 10% or more compared to the octane properties exhibited by an analogous fuel formulation which does not contain the same blend of components in the specified amounts as the fuel formulations of the present invention.
• Oxidation Stability - Potential Gum ASTM D873 Oxidation Stability - Lead Precipitate: ASTM D873 Water Reaction - Volume change: ASTM D1094 Detail Hydrocarbon Analysis (ASTM 5134) Examples 1-15
• Aviation fuel compositions of the invention were prepared by blending a base fuel, aniline and co-solvent.
• the base fuel was a blend of 20%v isopentane, 52%v light aviation alkylate and 28%v toluene and had the properties shown in Table 1 below.
• the acetate and isobutanol were mixed and then added to the blend as one component.
• the fuel compositions were prepared by blending base fuel, co-solvent and aniline, in that order, in amounts set out in Tables 3-6 below. After mixing, each blend was mechanically stirred for 2 to 3 minutes and was then sent for MON (ASTM D2700) and Distillation (ASTM D86) testing.
• Further fuel compositions were prepared having the compositions set out in Table 9 below.
• the same preparation method was used as in Examples 1-15 above.
• Various branched chain alcohols were used as a co-solvent as indicated in combination with n-butyl acetate.
• the alcohols used were isobutyl alcohol (IBA), isopentyl (IPA), isohexyl alcohol (IHexA), isoheptyl (IHepA), isooctyl alcohol (IOA).
• IBA isobutyl alcohol
• IPA isopentyl
• IHexA isohexyl alcohol
• IHepA isoheptyl
• IOA isooctyl alcohol
• the MON of Examples 16-20 are shown in Table 9 below.

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