Classifications

• • 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
  • C10L1/04—Liquid carbonaceous fuels essentially based on blends of hydrocarbons
  • C10L1/06—Liquid carbonaceous fuels essentially based on blends of hydrocarbons for spark ignition
• • 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
  • C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
  • C10L1/023—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only for spark ignition

Definitions

• the present invention relates to fuel compositions and in particular aviation gasolines possessing a high octane number suitable for use in piston-driven aircraft. If a gasoline engine is run on a fuel which has an octane number lower than the minimum requirement for the engine, knocking will occur. Straight run gasoline has a low motor octane number but may be boosted to the required motor octane number of 82-88 for automotive use by the addition of octane boosters such as tetraethyl lead either alone or with refinery components such as reformate, alkylate, cracked spirit or chemical streams such as toluene, xylene, methyl tertiary butyl ether or ethanol.
• octane boosters such as tetraethyl lead either alone or with refinery components such as reformate, alkylate, cracked spirit or chemical streams such as toluene, xylene, methyl tertiary butyl ether or ethanol.
• Aircraft piston-driven engines operate under extreme conditions to deliver the desired power e.g. high compression ratios. Due to the severity of the conditions e.g. with turbo charging or super charging the engine, aviation piston-driven engines require fuel of a minimum octane level higher than that for automotive internal combustion gasoline engines, in particular at least 98- 100.
• the base fuel of an aviation gasoline has a motor octane number of 90-93. To boost the motor octane number sufficiently to the required level, tetraethyl lead is added to the aviation base fuel.
• the fuel may contain the organolead and also other octane boosters, such as those described above. Industrial and Engineering Chemistry Vol. 36 No.
• tetraethyl lead is always used to boost the octane quality of the aviation gasoline to the desired level.
• Conventional octane boosters such as ethers, aromatics, such as toluene, and non- lead metal compounds can boost the motor octane number of unleaded motor gasoline sufficiently high enough to achieve the desired value but they do not boost the motor octane number of an unleaded aviation gasoline sufficiently high enough to ensure satisfactory performance or suffer from other significant technical limitations.
• US 5470358 describes the use of aromatic amines to boost the motor octane number of unleaded aviation gasoline to at least 98 but many aromatic amines are known to be toxic. They have high boiling points, no supercharge properties and high freezing points; they are also prone to produce gums.
• an unleaded aviation fuel composition having a Motor Octane Number of at least 98, and usually a final Boiling Point of less than 170°C, and preferably a Reid Vapour Pressure at 37.8°C of between 38-60 kPascals, which comprises: component (a) at least one hydrocarbon having the following formula I R-CH 2 -CH(CH3)-C(CH 3 ) 2 -CH3 I wherein R is hydrogen or methyl and component (b) at least one saturated liquid aliphatic hydrocarbon having 4 to 10 in particular 5 or 6 carbon atoms optionally with at least one other saturated liquid aliphatic hydrocarbon having from 5 to 10 carbon atoms wherein at least 30% by volume of the total composition is a hydrocarbon of formula I.
• IfR is hydrogen the hydrocarbon is triptane. If R is methyl the hydrocarbon is 2,2,3 trimethylpentane. Especially preferred is triptane. Triptane and 2,2,3 trimethylpentane may be used individually or in combination with each other, for example, in a weight ratio of 10:90 - 90:10, preferably, 30:70 - 70:30.
• the composition may comprise apart from a component (I), the hydrocarbon of formula I, a component (II) which is at least one of the known octane boosters described above especially an oxygenate octane booster, usually an ether, usually of Motor Octane Number of at least 96-105 e.g. 98-103.
• the ether octane booster is usually a dialkyl ether, in particular an asymmetric one, preferably wherein each alkyl has 1-6 carbons, in particular one alkyl being a branched chain alkyl of 3-6 carbons in particular a tertiary alkyl especially of 4-6 carbons such as tert-butyl or tert-amyl, and with the other alkyl being of 1-6 e.g. 1-3 carbons, especially linear, such as methyl or ethyl.
• component (II) include methyl tertiary butyl ether, ethyl tertiary butyl ether and methyl tertiary amyl ether.
• the oxygenate may also be an alcohol of 1-6 carbons e.g. ethanol.
• At least one component (I) may be present together with at least one component (II) in a combination.
• the combination may be, for example, triptane together with methyl tertiary butyl ether.
• the combination may be in a volume ratio of 40:60 to 99: 1 e.g. 50:50 to 90 : 10, preferably 60:40 to 85:15.
• the volume percentage of ether may be up to 30% of the total composition e.g. 1-30%, such as 1-15% or 5-25%.
• the motor octane number of the aviation gasoline of the invention is at least 98, for example 98-103, preferably 99 to 102. Motor Octane Numbers are determined according to ASTM D 2700-92.
• the hydrocarbons of formula I may also, especially when present in amount of at least 30% by volume, be used to provide gasolines of the invention with a Performance Number (according to ASTM D909) of at least 130 e.g. 130-170.
• Triptane or 2,2,3 trimethylpentane may be used in a purity of at least 95% but is preferably used as part of a hydrocarbon mixture obtained, via distillation of a cracked residue, which is an atmospheric or vacuum residue from crude oil distillation, to give a C4 fraction containing olefin and hydrocarbon, alkylation to produce a C4.9 especially a Cg.o fraction which is distilled to give a predominantly Cg fraction, which usually contains trimethyl pentanes including 223 trimethyl pentane and/or 233 trimethyl pentane.
• this fraction can be demethylated to give a crude product comprising at least 5% of triptane, which can be distilled to increase the triptane content in the mixture; such a distillate may comprise at least 10% or 20% of triptane and 2,2,3 trimethylpentane but especially at least 50% e.g. 50-90% the rest being predominantly of other aliphatic C7 and C8 hydrocarbons e.g. in amount 10-50% by volume.
• triptane and 2,2,3 trimethylpentane may be used in any commercially available form.
• the invention will be further described with triptane exemplifying the compound of formula I but 2,2,3 trimethylpentane may be used instead or as well.
• the amount of the hydrocarbon of Formula I alone or with component II may be present in the composition in an effective amount to boost the Motor Octane Number to at least 98 and may be in a percentage of from 35-92%, preferably 60-90%, especially 70-90% by volume, based on the total volume of the composition.
• the compound of formula I is usually in the composition in a percentage of 5-90%, 10-80%, 20-60% more especially 30-50% by volume, based on the total composition, though amounts of the compound of formula I of 10-45% are also very valuable; preferred are 20-90% or 40-90% or 50-90% by volume.
• the composition also comprises a component (b).
• Component (b) is at least one saturated aliphatic liquid hydrocarbon of 4 to 10 preferably 5 to 8 in particular 5 or 6 carbon atoms, alone or with at least one saturated aliphatic liquid hydrocarbon (different from component(a)) having from 4 to 10 carbons in particular 5 to 10 carbon atoms, preferably 5 to 8 carbon atoms, especially in combination with one of 4 carbons.
• Component (b) may comprise a component (III) which is more volatile and has a lower boiling point than component (a) in particular one boiling at least 30°C such as 30-60°C below that of triptane at atmospheric pressure, and especially is itself of Motor Octane Number greater than 88 in particular at least 90 e.g.
• component (III) examples include alkanes of 5 carbons in particular iso-pentane, which may be substantially pure or a crude hydrocarbon fraction from alkylate or isomerate containing at least 30%) e.g. 30-80% such as 50-70%, the main contaminant being up to 40% mono methyl pentanes and up to 50% dimethyl butanes.
• Component (III) of boiling point 30-60°C less than that of triptane may be used as sole component (III) but may be mixed with an alkane of boiling point 60-100°C less than that of triptane e.g. n and/or iso butane in blends of 99.5:0.5 to 70:30, e.g.
• Iso-pentane alone or mixed with n-butane is preferred, especially in the above proportions, and in particular with a volume amount of butane in the composition of up to 3.5%) e.g. 1-3.5% or 2-3.5%.
• Component (b) may also comprise a component (IV) having a boiling point higher than component (a) preferably one boiling at least 20°C more than the compound of formula I e.g. triptane such as 20-60°C more than triptane but less than 170°C and usually is of Motor Octane Number of at least 92 e.g. 92-100; such components (IV) are usually alkanes of 7-10 carbons especially 7 or 8 carbons, and in particular have at least one branch in their alkyl chain, in particular 1-3 branches, and preferably on an internal carbon atom and especially contain at least one - C(CH 3 ) - group.
• An example of component (IV) is iso-octane.
• Component (b) may be a combination of at least one component (III) together with at least one component (IV).
• the combination may be, for example, butane or isopentane together with iso-octane, and the combination may be in a volume ratio of 10 : 90 to 90 : 10, preferably 10:50 to 50:90, especially 15:85 to 35:65, in particular with butane or especially isopentane together with iso-octane.
• isopentane together with iso-octane in particular, in the above proportions, and optionally butane.
• triptane and isopentane and optionally n- butane are present in the composition of the invention with 80-90%) triptane and in particular in relative volume ratios of 80-90: 10-15:0-3.5.
• component (a) is 2,2,3 trimethylbutane and component (b) is isopentane in combination with iso-octane, preferably in relative volume ratios of 10-80 : 5-25 : 10:80 in particular 30-50 : 5- 25 : 35-60 or 15-45 : 10-18 : 45-75 or 60-80 : 10-18 : 10-25.
• the composition contains 30-80% of triptane and the isopentane and iso-octane are in a volume ratio of 35-15 : 65-85.
• the composition comprises component (a) as 2,2,3 trimethylbutane, methyl tertiary butyl ether and component (b) as isopentane in combination with n-butane, preferably in relative volume ratios of 50-90 : 5-30 : 10-15 : 0.1-3.5 in particular 50-80 : 10-25 : 10- 15 : 0.1-3.5.
• the composition may comprise an aromatic liquid hydrocarbon of 6-9 e.g. 6-8 or 7-9 carbons, such as xylene or a trimethyl benzene, preferably but toluene, in particular in amounts of up to 30% by volume of the total composition e.g. 1-30%) or 5-15%.
• a preferred embodiment is a composition that may thus contain 50-95% e.g. 50-80% triptane, 5-25% e.g. 10-25% component (b) e.g. isopentane and 5-30%, for example toluene.
• the benzene content of the composition is preferably less than 0.1% by volume.
• composition may comprise both the aromatic hydrocarbon and the ether.
• a preferred composition may comprise 45-80% triptane 5-30% ether (with a preferred total of both of 70-85%), 10-25%) component (b) (III) e.g. iso-pentane (optionally containing butane) and 5- 20% toluene, all by volume.
• compositions may also comprise 10-90% e.g. 25-85%, 35-80%, or 35- 90%) by volume of triptane, 5-75% e.g. 8-55% by volume of a mixture predominantly of iso C ⁇ and iso Cg hydrocarbons, but usually with small amounts of iso Cg and iso Co hydrocarbons and 5-40% e.g. 8-40% or 5-35% or 8-25% by volume isopentane.
• the triptane and mixture may be obtained as a distillation fraction obtained by the processing of crude oil and subsequent reactions as described above.
• the unleaded aviation gasoline composition of the invention usually has a calorific value (also called Specific Energy) of at least 42MJ/kg (18075 BTU/lb) e.g.
• the gasoline usually has a boiling range (ASTM D86) of 25-170°C and is usually such that at 75°C 10-40% by volume is evaporated, at 105°C a minimum of 50% is evaporated, at 135°C a minimum of 90% is evaporated; the final boiling point is usually not more than 170°C preferably 80-130°C.
• the gasoline usually has a maximum freezing point of -60°C in particular -40°C.
• the Reid Vapour Pressure of the gasoline at 37.8°C measured according to ASTM D323 is usually 30-60kPa preferably 38-60 e.g. 38-55 or especially 38-49 or 45-55kPa.
• the composition of the invention may contain at least one aviation gasoline additive, for example as listed in ASTM D-910 or DEF-STAN 91-90;
• additives are anti-oxidants, corrosion inhibitors, anti-icing additives e.g. glycol ethers or alcohols and anti-static additives, especially antioxidants such as one or more hindered phenols; in particular the additives may be present in the composition in amounts of 0.1-1 OOppm e.g. l-20ppm, usually of an antioxidant especially one or more hindered phenols.
• a coloured dye may also be present to differentiate the aviation gasoline from other grades of fuel.
• compositions of the invention are unleaded and have reduced toxicity, and are suitable for use in aviation gasoline for piston engine aircraft.
• Aromatic amines e.g. m-toluidine are usually substantially absent.
• An unleaded aviation gasoline was made by mixing 2,2,3 trimethylbutane of 99%) purity with iso-pentane and iso-octane to give a composition consisting of 2,2,3 trimethylbutane 40%, isopentane 12%>, and iso-octane 48% expressed in volume percentages of the total gasoline.
• Example 2 An unleaded aviation gasoline contained the gasoline of Ex.1 with 8mg/l of a mixture of 75%> 2,6-ditertiary, butyl phenol and 25% tertiary and tri tertiary, butyl phenols, as antioxidant.
• Example 3
• An unleaded aviation gasoline was made from a crude triptane fraction.
• a cracked residue from the distillation of crude oil was distilled to give a C4 fraction containing olefin and saturates.
• the fraction was alkylated (i.e. self reacted) to form a crude Cg saturate which was distilled to give a fraction boiling 95-120°C, which contained 223 and 233 trimethyl pentane.
• This fraction was demethylated by reduction to give a first fraction containing about 17% triptane and 83%> iso Cg- C9 with a majority of iso C ⁇ and iso Cg hydrocarbons.
• This first fraction was redistilled to produce a second fraction of 87%> triptane and 13% ⁇ iso C7 and Cg.
• Example 3 The process of Example 3 was repeated with the first fraction containing the 17%) triptane redistilled to give a third fraction containing 37% triptane and 63%) iso C ⁇ and Cg. 82 parts by volume of this third fraction were mixed with 18 parts of isopentane to give an unleaded aviation gasoline of MON value 98.0. Addition of the phenol mixture as in Ex.3 gave an oxidation stabilised aviation gasoline fuel. Examples 5-9 In these Examples 2,2,3 trimethylbutane (triptane) 99% purity was mixed with iso- pentane and butane, and optionally toluene and/or methyl tertiary butyl ether, to produce a series of gasoline blends, for making unleaded aviation gasolines.
• the formulated gasolines were made by mixing each blend with a phenolic antioxidant 55% minimum 2,4 dimethyl-6-tertiary butyl phenol 15% minimum 4 methyl-2, 6-ditertiary-butyl phenol with the remainder as a mixture of monomethyl and dimethyl-tertiary butyl phenols (DEF STAN 91-90 RDE/A/610).
• T 10% means the temperature at which 10% by volume of the composition has distilled.

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• Chemical & Material Sciences (AREA)
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• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Liquid Carbonaceous Fuels (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)

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• 1996
  • 1996-11-18 GB GBGB9623934.8A patent/GB9623934D0/en active Pending
• 1997
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