Fuel and related compositions – Liquid fuels – Aluminum or heavy metal – other than lead – containing
Reexamination Certificate
1998-12-21
2001-07-10
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Aluminum or heavy metal, other than lead, containing
C044S426000, C044S449000
Reexamination Certificate
active
06258134
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to aviation gasoline (Avgas) compositions and methods of making and using such compositions. More particularly, the present invention concerns high octane Avgas compositions containing a non-leaded additive package and methods of making and using such compositions.
Conventional aviation gasoline (Avgas) generally contains an aviation alkylate basefuel and a lead-based additive package. The industry standard Avgas known as 100 Low Lead (100LL) contains the lead additive tetraethyllead (TEL) for boosting the anti-knock property of the Avgas over the inherent anti-knock property of its aviation alkylate basefuel. Knocking is a condition of piston-driven aviation engines due to autoignition, the spontaneous ignition of endgases (gases trapped between the cylinder wall and the approaching flame front) in an engine cylinder after the sparkplug fires. A standard test that has been applied to measure the anti-knock property of lead-based Avgas under various conditions is the motor octane number (MON) rating test (ASTM D2700). Another standard test applied to lead-based Avgas is the supercharge (performance number) rating test (ASTM D909).
Despite the ability of lead-based Avgas to provide good anti-knock property under the severe demands of piston-driven aviation engines, such lead-based compositions are meeting stricter regulations due to their lead and lead oxide emissions. Current U.S. regulations set a maximum amount of TEL for aviation fuels at 4.0 ml/gal and concerns for the negative environmental and health impact of lead and lead oxide emissions may effect further restrictions. Gaughan (PCT/US94/04985, U.S. Pat. No. 5,470,358) refers to a no-lead Avgas containing an aviation basefuel and an aromatic amine additive. The Avgas compositions exemplified in Gaughan reportedly contain an aviation basefuel (e.g., isopentane, alkylate and toluene) having a MON of 92.6 and an alkyl- or halogen-substituted phenylamine that boosts the MON to at least about 98. Gaughan also refers to other non-lead octane boosters such as benzene, toluene, xylene, methyl tertiary butyl ether, ethanol, ethyl tertiary butyl ether, methylcyclopentadienyl manganese tricarbonyl and iron pentacarbonyl, but discourages their use in combination with an aromatic amine because, according to Gaughan, such additives are not capable by themselves of boosting the MON to the 98 level. Gaughan concludes that there is little economic incentive to combine aromatic amines with such other additives because they would have only a very slight incremental effect at the 98 MON level.
It would be desirable to find alternative Avgas compositions that avoid the use of lead-based additives and have good performance in piston-driven aviation engines. It would also be desirable to find Avgas compositions that could use less expensive basefuels.
SUMMARY OF THE INVENTION
The Avgas compositions of the invention contain a combination of non-lead additives (also referred to as the “additive package”) including an alkyl tertiary butyl ether and an aromatic amine. The additive package may further include manganese, for example, as provided by methyl cyclopentadienyl manganese tricarbonyl (MT). In a preferred embodiment, the substantially positive or synergistic additive package is combined with a wide boiling range alkylate basefuel. In a further preferred embodiment, the inventive Avgas composition is an unleaded Avgas having good performance in a piston-driven aviation engine as determined by one or more ratings including MON, Supercharge and Knock Cycles/Intensity at maximum potential knock conditions of an aviation engine.
The invention is also directed to a method of making an unleaded Avgas composition wherein the additive package is combined with a basefuel, such as a wide boiling range alkylate. The concentration of the additives in the Avgas may be based on a non-linear model, wherein the combination of additives has a substantially positive or synergistic effect on the performance of the unleaded Avgas composition. The invention is further directed to a method of improving aviation engine performance by operating a piston-driven aviation engine with such Avgas compositions.
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Derwent Abstract (AN 97-098600) referring to Russian patent RU2061736 (Jun. 10, 1996) and Russian patent application RU940017595 (May 11, 1994) (Achinsk Oil Refinery Stock Co).
English-language translation of Russian patent document RU2061736 (Jun. 10, 1996) (Achinsk Oil Refinery Stock Co.).
Valentine et al., “Developing a High Octane Unleaded Aviation Gasoline,”SAE International Meeting&Exposition(1997) Month Unknown.
Database WPI, Derwent Abstract No. 97-098600, for patent document assigned to Achinsk Oil Refinery Stock Co., entitled “Hydrocarbon Composition for IC Engine with Spark Ignition Containing (Alpha-hydroxy-isopropyl)ferrocene, Methyl-t-butyl ether and/or N-methyl aniline and Hydrocarbon Fuel Giving Reduced Octane Number.”.
Campbell Teddy G.
Dorn Peter
Liiva Peter M.
Studzinski William M.
Valentine Joseph N.
Howrey Simon Arnold & White
Medley Margaret
Reinisch Morris N.
Texaco Inc.
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