HIGH OCTANE UNLEADED AVIATION GASOLINE

Abstract

Concentrate for the manufacture of unleaded aviation gasoline. High quality aviation alkylate, or similar base fuel is blended with selected aromatic solvents, including alkyl benzenes effective to improve the functional engine performance to avoid harmful detonation in aircraft piston engines. Monoalkylated benzenes such as toluene and ethylbenzene are utilized in combination with dialkylated benzenes, such as xylenes. Aromatic amines, for example p-toluidine and m-toluidine, may be added to increase MON. Alcohols such as ethanol and/or methanol may be added in effective amounts to produce unleaded AVGAS which meets a required freeze point. Amounts of toluene to p-toluidine, and/or of the amount of p-toluidine to m-toluidine may be in a controlled ratio in amounts effective to produce unleaded AVGAS which meets a required freeze point. Isopentane and/or butane may be included to provide a required vapor pressure profile.

Claims

1. A concentrate for the manufacture of high octane unleaded aviation gasoline, said concentrate comprising: (a) one or more aromatic solvents, said aromatic solvents comprising not more than about fifty percent (50%) by weight, at least one of said one or more aromatic solvents comprising toluene; and (b) one or more aromatic amines, said one or more aromatic amines being present, collectively, at not more than about fifty five percent (55%) by weight, wherein at least one of one or more aromatic amines comprises m-toluidine.

2. The concentrate as set forth in claim 1, wherein said one or more aromatic amines further comprises p-toluidine.

3. The concentrate as set forth in claim 1, further comprising one or more alcohols, said one or more alcohols comprising C.sub.1 to C.sub.3 alcohols.

4. The concentrate of claim 3, wherein said one or more alcohols comprises ethanol.

5. . The concentrate of claim 3, wherein said one or more alcohols consists essentially of ethanol.

6. The concentrate of claim 3, wherein said one or more alcohols comprises methanol.

7. The concentrate of claim 4, wherein said one or more alcohols further comprises methanol.

8. The concentrate of claim 1, wherein the weight ratio of aromatic solvent to aromatic amine is about 1:1, or more.

9. The concentrate of claim 8, wherein the amount of aromatic amine is at least thirty percent (30%) by weight of said concentrate.

10. The concentrate as set forth in claim 3, wherein the amount of said alcohols comprises about twenty percent (20%) or less by weight of said concentrate.

11. A concentrate for the manufacture of high octane unleaded aviation gasoline, said concentrate comprising: (a) one or more aromatic solvents, said aromatic solvents comprising not more than about fifty percent (50%) by weight, at least one of said one or more aromatic solvents comprising toluene at least about forty percent (1%) by weight of said concentrate; (b) two or more aromatic amines, said two or more aromatic amines being present, collectively, at not less than about thirty percent (30%) and not more than about forty percent (1%) by weight, wherein said aromatic amines consist essentially of p-toluidine and m-toluidine; and (c) further comprising one or more alcohols, said one or more alcohols elected from the group consisting of methanol and ethanol, and wherein said alcohols comprise collectively not more than about twenty percent (20%) of said concentrate.

12. The concentrate as set forth in claim 11, wherein said toluene comprises an amount that is from about 1:1 to about 2:1, by weight, compared to the amount of said p-toluidine.

13. The concentrate as set forth in claim 11, wherein said ethanol comprises an amount that is from about 1:4 to about 2:3, by weight, compared to the amount of said p-toluidine.

14. The concentrate as set forth in claim 11, wherein said concentrate comprises methanol, and wherein said methanol comprises an amount that is from about 1:4 to about 2:3, by weight, compared to the amount of said p-toluidine.

Description

DETAILED DESCRIPTION

[0030] Exemplary high octane unleaded aviation gasoline blend compositions are set forth herein. Methods for the preparation of such novel high octane unleaded aviation gasoline blends, and concentrate additive packages for use in methods for the manufacture of such novel high octane unleaded aviation gasoline blend(s) are provided. Such high octane unleaded gasolines have been developed as direct drop-in-substitutionsor at least for functional drop-in substitutionsand which provide equivalent performance in spite of minor deviations from standard ASTM specifications for aviation gasolines such as Grade 100LL. Generally, as the term is used herein, unleaded aviation gasoline refers to gasoline possessing the specific properties suitable for fueling aircraft powered by reciprocating spark ignition engines, where lead is not intentionally added at the point of manufacture or first shipment.

[0031] As described in my prior patent applications as noted above, as a result of testing of a novel unleaded aviation gasoline blend in a full scale aircraft engine test stand, as well as in a turbocharged aircraft in flight, I have discovered that it is possible to provide, in an embodiment, an unleaded aviation gasoline blend by mixing (1) an unleaded aviation gasoline base fuel (high grade aviation alkylate or commercial iso-octane or mixtures thereof), with (2) effective amounts of an alkylated benzenes, and particularly dialkyl benzenes such as various xylenes, to increase the detonation performance of the unleaded aviation gasoline blend when operated on a full scale aircraft engine to the equivalent, or better than, the full scale engine detonation performance of a Grade 10OLL avgas which minimally meets the octane rating requirements set forth in ASTM Standard D910. In other words, in an embodiment, novel unleaded aviation gasoline blend can be provided that are equivalent to the full scale engine performance of a Grade 100LL avgas which meets the minimum MON rating requirements set forth in ASTM D910. Further, such testing has determined that an unleaded aviation gasoline blend may be formulated that provides detonation performance when operated on full scale aircraft engines to approximately the equivalent of, or better than, the full scale engine detonation performance of a FBO Grade 100LL avgas having a selected MON. Such benefits are especially noticeable when the testing proceeds using standard ASTM test procedures at detonation performance conditions of wherein detonation performance is determined at detonation intensity levels of twenty (20) BAR, determined by calculating a moving average of the detonation intensities of at least 7 but not more than 20 consecutive combustion events, using test procedures set forth in ASTM D6424 to calculate the detonation intensity of each individual combustion event.

[0032] Thus, by testing the novel unleaded aviation gasoline blends described herein at load in an actual aircraft engine in a fully instrumented test stand, it was observed that, at least to some extent, the detonation performance on the full scale aircraft engine of certain novel unleaded aviation gasoline blends exceeds the detonation performance which would be expected for such blends based on MON test results, or other existing test standards (e.g. the ASTM D 2700 motor octane test required under ASTM Standard D910). Again, such beneficial performance is especially noticeable when the detonation performance is determined at detonation intensity levels of twenty (20) BAR, determined by calculating a moving average of the detonation intensities of at least 7 but not more than 20 consecutive combustion events, using test procedures set forth in ASTM D6424 to calculate the detonation intensity of each individual combustion event.

[0033] Such beneficial synergistic effect seems to especially manifest itself as demonstrated in full scale aircraft engine detonation performance testing in the case of novel unleaded aviation fuel blends which include alkylated benzenes having methyl groups in a meta-ring position. For example, using a mixture of 1,3-dimethylbenzene (meta-xylene) and 1,4 dimethylbenzene (para-xylene), in amounts when added together amounts to slightly less than about half, by weight (e.g. up to a maximum of forty five percent (45%) by weight) of the total unleaded aviation gasoline blend in connection with other constituents as described herein may provide the necessary performance properties. However, various other alkylated benzenes, such as ethyl benzene and ortho-xylene, may compose a portion of such mixture in order to facilitate commercially economical production and meet overall fuel blend performance objectives.

[0034] However, when I investigated commercially available components that might be useful for increasing the motor octane number (MON) of a final unleaded aviation gasoline blend in a cost effective manner, I found that it appears unlikely that a sufficient supply of m-toluidine would be available, at least in the short term, to provide adequate quantities to support the widespread manufacture of a new high octane unleaded gasoline that contained appreciable amounts of m-toluidine. And, although I was aware that the octane enhancing properties of p-toluidine were well known, due to the relatively high melting point (plus forty four degrees Centigrade (+44 C.)) for p-toluidine as compared to the melting point of m-toluidine (minus thirty degrees Centigrade (-30 C.)), the use of p-toluidine has heretofore been generally considered undesirable in aviation gasolines, at least in any appreciable quantities, at least for fuel blends compatible with extremely cold storage and operating conditions which are routine for aircraft. Moreover, given that the toludine isomers are produced at present in ratios of roughly 60% o-toluidine, 36% p-toluidine, and 4% m-toluidine, it is clear that finding a way to use other octane enhancing aromatic amines, such as p-toluidine, would solve a key soppy chain barrier which, in part, may currently prevent the widespread adoption of a high octane unleaded aviation gasoline. And, although the o-toluidine isomer has a desirable minus 28 degrees Centigrade (28 C.) melting point, its undesirable toxicity characteristics are generally believed likely to prevent its use in a desirable high octane unleaded aviation gasoline.

[0035] I have now discovered that by adopting the use of certain co-solvents, it is possible to use appreciable quantities of p-toluidine in a high octane unleaded gasoline, while maintaining freeze point protection to extremely low freezing point conditions. The use of such co-solvents also enables efficient manufacturing of a high octane unleaded aviation gasoline, as well as the development of concentrate additive packages for use in a method of distributed manufacture of a high octane unleaded aviation gasoline. In various embodiments, one or more aromatic amines, including p-toluidine, may be utilized. In various embodiments, an effective amount of such one or more aromatic amines may be utilized to increase the MON, in order to provide a knock value, as Motor Octane Number (MON) of at least 99.6, as measured by the ASTM D2700 Test Method. In an embodiment, the amount of aromatic amines provided may be somewhere in the range from more than zero up to a maximum of about four point five percent (4.5%) by weight in the final high octane unleaded gasoline. In an embodiment, the amount of aromatic amines provided may be somewhere in the range from more than zero up to a maximum of about six percent (6.0%) by weight. In an embodiment, a combination of aromatic amines may be selected for use in a high octane unleaded fuel blend. In an embodiment, a suitable combination of aromatic amines may include m-toluidine (also known as meta-toluidine) and p-toluidine (also known as para-toluidine). The use of the combination of aromatic amines, including p-toluidine, solves a significant problem which was faced when trying to develop a commercially viable high octane unleaded aviation gasoline, namely how can commercially reasonable quantities of octane enhancing aromatic amine constituents be obtained and utilized in an unleaded aviation gasoline in which performance and freeze point requirements are assured.

[0036] In developing novel high octane unleaded gasoline compositions which satisfy both detonation performance requirements and freeze point protection requirements, I conducted a series of tests. Various embodiments for the composition of a suitable high octane unleaded aviation gasoline were evaluated. Candidate compositions from twenty of such tests are set forth in TABLE 1 (compositions from tests No. 1 through No. 10) and in TABLE 2 (compositions from tests No. 11 through No. 20).

[0037] The Base High Aromatic Unleaded Gasoline used as the base fuel in the tests did not include aromatic amines, alcohols, or toluene therein. The base fuel formulation used for testing included (a) a xylol mixture base in the amount of 46.6 percent by weight, (b) high grade alkylate in the amount of 38.3 percent by weight, (c) isopentane in the amount of 6.8% by weight, and (d) butane in the amount of 4.7% by weight. More specific details on xylol mixture formulation is noted below, and the reader is further referred to the xylol specification provided by ASTM. The noted aromatic amine additives that were tested, namely p-toluidine (p-T) and m-toluidine (m-T), can be blended with one or more diluents or carrier fluids (as tested, toluene, and also ethanol and/or methanol), and can then be admixed with the base fuel gasoline formulation. Such a procedure may be useful in a concentrate additive package, for use in manufacture of a high octane unleaded aviation gasoline, as further noted below. The concentration of solvents such as toluene, ethanol, and the like in a concentrate additive package to be admixed with the base fuel gasoline must be taken into account in any final unleaded aviation gasoline composition, and the effective amount of additives to form the final gasoline composition adjusted accordingly.

[0038] Test No. 1 included a base fuel at 91.4%, toluene at 5.0%, p-toluidine at 2.6%, m-toluidine at 0.5%, no ethanol, and methanol at 0.5%. The ratio of toluene to p-toluidine was 1.92. The ratio of p-toluidine to m-toluidine was 5.20. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 57 C.

[0039] Test No. 2 included a base fuel at 90.9%, toluene at 5.0%, p-toluidine at 2.6%, m-toluidine at 0.5%, no ethanol, and methanol at 1.0%. The ratio of toluene to p-toluidine was 1.90. The ratio of p-toluidine to m-toluidine was 5.24. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 63.3 C.

[0040] Test No. 3 included a base fuel at 91.4%, toluene at 5.0%, p-toluidine at 2.6%, no m-toluidine, ethanol at 1.0%, and no methanol. The ratio of toluene to p-toluidine was 1.92. There was no m-toludine, so the ratio of p-toluidine to m-toluidine was not reported. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 62.0 C.

[0041] Test No. 4 included a base fuel at 90.0%, toluene at 4.9%, p-toluidine at 3.6%, m-toluidine at 0.5%, ethanol at 1%, and no methanol. The ratio of toluene to p-toluidine was 1.36. The ratio of p-toluidine to m-toluidine was 7.35. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 56.0 C.

[0042] Test No. 5 included a base fuel at 89.4%, toluene at 4.9%, p-toluidine at 3.7%, m-toluidine at 0.5%, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 1.32. The ratio of p-toluidine to m-toluidine was 7.55. The formulation was found to be NOT cloudy at 66.0 C.

[0043] Test No. 6 included a base fuel at 90.0%, toluene at 4.9%, p-toluidine at 3.5%, m-toluidine at 0.5%, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 1.40. The ratio of p-toluidine to m-toluidine was 7.14. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 59.8 C.

[0044] Test No. 7 included a base fuel at 92.8%, toluene at 5.1%, p-toluidine at 1.1%, no m-toluidine, ethanol at 1.0%, and no methanol. The ratio of toluene to p-toluidine was 4.64. The ratio of p-toluidine to m-toluidine was not reported, since there was no m-toluidine. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 59.0 C.

[0045] Test No. 8 included a base fuel at 92.3%, toluene at 5.1%, p-toluidine at 1.1%, no m-toluidine, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 4.64. The ratio of p-toluidine to m-toluidine was not reported, since there was no m-toluidine. The formulation was found to be NOT cloudy at 67.0 C.

[0046] Test No. 9 included a base fuel at 91.4%, toluene at 5.0%, p-toluidine at 2.1%, no m-toluidine, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 2.38. The ratio of p-toluidine to m-toluidine was not reported, since there was no m-toluidine. The formulation was found to be NOT cloudy at 65.0 C.

[0047] Test No. 10 included a base fuel at 90.5%, toluene at 4.9%, p-toluidine at 3.1%, no m-toluidine, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 1.58. The ratio of p-toluidine to m-toluidine was not reported, since there was no m-toluidine. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 56.0 C.

[0048] Test No. 11 included a base fuel at 90.0%, toluene at 4.9%, p-toluidine at 3.1%, no m-toluidine, ethanol at 2.0%, and no methanol. The ratio of toluene to p-toluidine was 1.58. The ratio of p-toluidine to m-toluidine was not reported, since there was no m-toluidine. The formulation was found to be NOT cloudy at 64.5 C.

[0049] Test No. 12 included a base fuel at 89.3%, toluene at 4.80%, p-toluidine at 4.0%, no m-toluidine, ethanol at 1.9%, and no methanol. The ratio of toluene to p-toluidine was 1.20. The ratio of p-toluidine to m-toluidine was no reported since there was no m-toluidine. The formulation was found to be cloudy (reached the freezing point where certain components froze from the solution) at 46.0 C.

[0050] Test No. 13 included a base fuel at 88.0%, toluene at 4.8%, p-toluidine at 4.0%, m-toluidine at 0.5%, ethanol at 1.9%, and no methanol. The ratio of toluene to p-toluidine was 1.20. The ratio of p-toluidine to m-toluidine was 8.00. The formulation was found to be NOT cloudy at 64.0 C.

[0051] Test No. 14 included a base fuel at 90.9%, toluene at 4.0%, p-toluidine at 3.1%, m-toluidine at 0.5%, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 1.29. The ratio of p-toluidine to m-toluidine was 6.33. The formulation was found to be cloudy at 60.0 C.

[0052] Test No. 15 included a base fuel at 89.6%, toluene at 4.9%, p-toluidine at 3.0%, m-toluidine at 0.5%, ethanol at 2.0%, and no methanol. The ratio of toluene to p-toluidine was 1.63. The ratio of p-toluidine to m-toluidine was 6.12. The formulation was found to be cloudy at 60.0 C.

[0053] Test No. 16 included a base fuel at 91.9%, toluene at 5.0%, p-toluidine at 2.6%, m-toluidine at 0.5%, no ethanol, and no methanol. The ratio of toluene to p-toluidine was 1.92. The ratio of p-toluidine to m-toluidine was 5.10. The formulation was found to be cloudy at 54.0 C.

[0054] Test No. 17 included a base fuel at 91.3%, toluene at 5.0%, p-toluidine at 2.6%, m-toluidine at 0.5%, no ethanol, and methanol at 0.5%. The ratio of toluene to p-toluidine was 1.91. The ratio of p-toluidine to m-toluidine was 5.28. The formulation was found to be cloudy at 54.0 C.

[0055] Test No.18 included a base fuel at 90.4%, toluene at 5.0%, p-toluidine at 2,6%, m-toluidine at 0.5%, ethanol at 1.5%, and no methanol. The ratio of toluene to p-toluidine was 1.90. The ratio of p-toluidine to m-toluidine was 5.24. The formulation was found to be cloudy at 61.0 C.

[0056] Test No.19 included a base fuel at 90.0%, toluene at 4.9%, p-toluidine at 2.6%, m-toluidine at 0.5%, ethanol at 2.0%, and no methanol. The ratio of toluene to p-toluidine was 1.88. The ratio of p-toluidine to m-toluidine was 5.22. The formulation was found to be cloudy at 63.0 C.

TABLE-US-00001 TABLE 1 % Base High Aromatic UL Gasoline (G100UL) w/o aromatic amines, Fz Point alcohol, or % % % % % CLEAR CLOUDY ratio ratio Test # toluene Toluene pT mT Ethanol Methanol AT AT Toluene/pT pT/mT 1 91.4 5.0 2.6 0.5 0.0 0.5 NR 57 C. 1.92 5.20 2 90.9 5.0 2.6 0.5 0.0 1.0 63.0 C. 63.3 C. 1.90 5.24 3 91.4 5.0 2.6 0.0 1.0 0.0 60.0 C. 62.0 C. 1.92 4 90.0 4.9 3.6 0.5 1.0 0.0 55.0 C. 56.0 C. 1.36 7.35 5 89.4 4.9 3.7 0.5 1.5 0.0 66.0 C. <66.0 C. 1.32 7.55 6 90.0 4.9 3.5 0.5 1.5 0.0 58.0 C. 59.8 C. 1.40 7.14 7 92.8 5.1 1.1 0.0 1.0 0.0 58.0 C. 59.0 C. 4.64 8 92.3 5.1 1.1 0.0 1.5 0.0 67.0 C. <67.0 C. 4.64 9 91.4 5.0 2.1 0.0 1.5 0.0 65.0 C. <65.0 C. 2.38 10 90.5 4.9 3.1 0.0 1.5 0.0 NR 56.0 C. 1.58

TABLE-US-00002 TABLE 2 % Base High Aromatic UL Gasoline (G100UL) w/o aromatic amines, alcohol, or Fz Point toluene % % % % % CLEAR CLOUDY ratio ratio Test # w/o mT or pT Toluene pT mT Ethanol Methanol AT AT Toluene/pT pT/mT 11 90.0 4.9 3.1 0.0 2.0 0.0 64.5 C. NR 1.58 12 89.3 4.8 4.0 0.0 1.9 0.0 NR. 46.0 C. 1.20 13 88.8 4.8 4.0 0.5 1.9 0.0 64.0 C. NR 1.20 8.00 14 90.9 4.0 3.1 0.5 1.5 0.0 58.0 C. 60.0 C. 1.29 6.33 15 89.8 4.9 3.0 0.5 2.0 0.0 59.0 C. 60.0 C. 1.63 6.12 16 91.9 5.0 2.6 0.5 0.0 0.0 NR 54.0 C. 1.92 5.10 17 91.3 5.0 2.6 0.5 0.0 0.5 NR 54.0 C. 1.91 5.28 18 90.4 5.0 2.6 0.5 1.5 0.0 58.0 C. 61.0 C. 1.90 5.24 19 90.0 4.9 2.6 0.5 2.0 0.0 61.0 C. 63.0 C. 1.88 5.22 20 90.9 5.0 2.6 0.5 0.0 1.0 63.0 C. 64.0 C. 1.90 5.26

[0057] Test No.20 included a base fuel at 90.9%, toluene at 5.0%, p-toluidine at 2.6%, m-toluidine at 0.5%, no ethanol, and methanol at 1.0%. The ratio of toluene to p-toluidine was 1.90. The ratio of p-toluidine to m-toluidine was 5,26. The formulation was found to be cloudy at 64.0 C.

[0058] Thus, I have discovered that it is entirely possible to formulate a high octane unleaded aviation gasoline which is capable of meeting very low freeze point conditions, while utilizing as a component the previously thought undesirable component of p-toluidine. It is clear based on the above described testing that in various embodiments, a freezing point objective of 47.0 C. may be achieved. It is also clear based on the above described testing that in various embodiments, a freezing point objective of 58.0 C. may be achieved.

[0059] In various embodiments, a high octane unleaded aviation gasoline may be provided by using a selected base unleaded fuel, such as a high grade aviation alkylate having a selected motor octane number (MON). More generally, such base fuels used in aviation gasolines consist of blends of refined hydrocarbons, derived from crude petroleum, natural gasoline, or blends, thereof, with synthetic hydrocarbons or aromatic hydrocarbons, or both. In an embodiment, a high grade aviation alkylate would be one composed primarily of isooctane (2,2,4-trimethylpentane) and the isomers thereof, and other components that results through the typical refinery alkylation units. Such high grade aviation alkylates may more generally be defined as including those base fuels which have a motor octane number (MON) of at least 96. In other embodiments, a high grade aviation alkylate may have a motor octane number (MON) of 97 or better. In other embodiments, a high grade aviation alkylate may have a motor octane number (MON) of 98 or better.

[0060] In various embodiments effective amounts of one or more dialkylbenzenes are mixed with the high grade aviation alkylate, or other similar base fuel. The one or more dialkylbenzenes may comprise meta-xylene, para-xylene, or ortho-xylene. In various embodiments, the meta-xylene and the para-xylene together comprise no more than about forty five percent (45%) by weight of the finished high octane unleaded aviation gasoline. In an embodiment, the para-xylene comprises no more than about thirteen percent (13%) by weight of the finished high octane unleaded aviation gasoline. In an embodiment, the ortho-xylene comprises no more than eleven percent (11%) by weight of the finished high octane unleaded aviation gasoline.

[0061] In various embodiments, two or more monoalkylated benzenes are mixed with the high grade aviation alkylate, or other similar base fuel. In an embodiment, the two or more monoalkylated benzenes include ethylbenzene and toluene. In an embodiment, the toluene may be provided at about ten percent (10%) or less of the finished high grade unleaded aviation gasoline. In an embodiment, the toluene may be provided at about six percent (6%) or less of the finished high grade unleaded aviation gasoline.

[0062] In various embodiments, aromatic amines are mixed with the high grade aviation alkylate, or other similar base fuel. In various embodiments, a selected amount of p-toluidine is provided. In various embodiments, a selected amount of p-toluidine may be provided in a range from more than zero percent (0%) to not more than six percent (6%) by weight of a finished high octane unleaded aviation gasoline. In various embodiments, the amount of toluene provided is in an amount that is equal to or greater than the amount of p-toluidine, by weight, in the finished high octane unleaded aviation gasoline. In various embodiments, the amount of toluene provided may be an amount that is from about 1:1 to about 2:1, by weight, compared to the amount of p-toluidine. In an embodiment, the amount of toluene provided may be an effective amount whereby a finished high octane unleaded aviation gasoline meets a freezing point requirement. In various embodiments, the amount of p-toluidine provided may be about four percent (4%) plus or minus one point five percent (1.5%) by weight of a finished high octane unleaded aviation gasoline. In such instance, the amount of toluene may comprise an amount that is equal to or greater than the amount of the p-toluidine, by weight; In various embodiments, the amount of p-toluidine provided may be about three point five percent (3.5%) plus or minus one point five percent (1.5%) by weight of a finished high octane unleaded aviation gasoline.

[0063] In various embodiments, a selected amount of m-toluidine may be provided. In some of such embodiments, the selected amount of m-toluidine may be from more than zero percent (0%) to not more than six percent (6%) by weight of said high octane unleaded aviation gasoline. In an embodiment, the amount of m-toluidine may be about one and one-half percent (1.5%) plus or minus about one point two-five percent (1.25%) by weight of a finished high octane unleaded aviation gasoline. In various embodiments, the selected amount of p-toluidine and the selected amount of m-toluidine is in a ratio, by weight, of between 2:1 and 8:1, respectively. In other embodiments, the selected amount of p-toluidine and said m-toluidine may be present in a ratio by weight of between 2.5:1 and 8:1, respectively. In various embodiments, an effective amount of m-toluidine may be provided to enable the high octane unleaded aviation gasoline to meet said freezing point.

[0064] In various embodiments, additional constituents are added to the high grade aviation alkylate, or other similar base fuel in amounts effective to achieve the extremely low freeze point requirements which may be established for a particular fuel. In an embodiment, such additional constituents may include a selected amount of one or more selected alcohols. In various embodiments, the selected amount of the one or more selected alcohols may comprise from more than zero percent (0%) to about six percent (6%) of the finished high octane unleaded aviation gasoline. In various embodiments, the selected one or more selected alcohols may include ethanol, and in such event, the ethanol may be present from more than zero percent (0%) to not more than six percent (6%) by weight of a finished high octane unleaded aviation gasoline. In various embodiments, the selected amount of the one or more selected alcohols may comprise from more than zero percent (0%) to about four percent (4%) of the finished high octane unleaded aviation gasoline. In various embodiments, the one or more selected alcohols may include methanol. In such a case, the selected amount of methanol may be from more than zero percent (0%) to not more than two percent (2%) by weight of a finished high octane unleaded aviation gasoline. In an embodiment, the selected alcohol may consist essentially of methanol, and in such case, the selected amount of methanol may be from zero percent (0%) to not more than two percent (2%) by weight of said high octane unleaded aviation gasoline. In an embodiment, the selected alcohol may be isopropyl alcohol. In an embodiment, an effective amount of a selected alcohol may be provided wherein the freezing point of a finished high octane unleaded aviation gasoline is minus forty seven degrees Centigrade (47 C.), or lower, as tested per ASTM standard D910 for Grade 100LL aviation gasoline. In an embodiment, an effective amount may be provided wherein the freezing point of a finished high octane unleaded aviation gasoline is minus fifty eight degrees Centigrade (58 C.), or lower, as tested per ASTM standard D910 for Grade 100LL aviation gasoline.

[0065] In various embodiments, the amount of ethanol provided may be an amount that is from about 1:4 to about 2:3, by weight, compared to the amount of p-toluidine. In various embodiments, the amount of methanol provided may be an amount that is from about 1:4 to about 2:3, by weight, compared to the amount of p-toluidine. In an embodiment, the selected alcohols may include ethanol and methanol, and wherein the total combined amount of ethanol and said methanol is from more than zero percent (0%) to not more than four percent (4%) by weight of a finished high octane unleaded aviation gasoline. In an embodiment, the one or more selected alcohols may consist essentially of methanol and ethanol, and in such instance, the amounts of methanol and said ethanol (taken together) may be from about 1:4 to about 2:3, by weight, compared to the amount of p-toluidine provided. In various embodiments, the amounts of the one or more selected alcohols may comprise an amount effective, in combination, so that the finished high octane unleaded aviation gasoline meets said freezing point.

[0066] Finally, as is generally known in the art of manufacture of aviation gasolines, butane and/or isopentane may be added to a high grade aviation alkylate, or other similar base fuel in amounts effective to achieve a desired vapor pressure curve. In an embodiment, a combination of effective amounts of butane and isopentane may be added wherein the vapor pressure in the finished high octane unleaded aviation gasoline is in the range between 38 kPa and 49 kPa, as measured using ASTM Standard D5191.

[0067] In an embodiment, a concentrate additive package may be provided for the manufacture of high octane unleaded aviation gasoline. In an embodiment, the concentrate may include (a) one or more aromatic solvents, said aromatic solvents, not more than about fifty percent (50%) by weight of the concentrate. In an embodiment, at least one of the one or more aromatic solvents includes toluene. In an embodiment, the amount of toluene may be at least about forty percent (40%) by weight of the concentrate.

[0068] Further, one or more aromatic amines are included in the additive package. The one or more aromatic amines may be present, collectively, at not more than about fifty five percent (55%) by weight. In an embodiment, the one or more aromatic amines will include m-toluidine. In an embodiment, the one or more aromatic amines will include p-toluidine. In an embodiment, the one or more aromatic amines will include both p-toluidine and m-toluidine. In an embodiment, two or more aromatic amines, may be present. In such case the two or more aromatic amines may be present, collectively, at not less than about thirty percent (30%) and not more than about forty percent (40%) by weight. In an embodiment, the aromatic amines may consist essentially of p-toluidine and m-toluidine.

TABLE-US-00003 TABLE 3 Fractions of total additive package. This additive, blend, or concentrate package would then constitute from approximately 7.5% to 15% of total final gasoline. Sample calculations Components for 10% and 15% are shown, but the Blend Package Blend Package of concentrate exact amount would be determined based as fraction of as fraction of for additive or on the desired final MON. total gasoline total gasoline blend package Ratios 0.100 0.150 components components Toluene 0.05 0.455 0.0455 0.0682 pT 0.035 0.318 0.0318 0.0477 *** mT 0.005 0.045 0.0045 0.0068 ethanol 0.02 0.182 0.0182 0.0273 Total 0.11 1.000 0.1000 0.1500 LOW SOLVENT CONCENTRATE: The package below would minimize the bulk volume, Then, additional alcohol would be added. In an embodiment, the concentrate would have only enough toluene to keep the pT In solution to a selected freeze point. Fractions of total additive package. This additive, or blend, package would then constitute from - 4 to 10% of total final fuel. Sample calculations for 6.24% and 9.5% are shown, but the exact amount would Blend Package Blend Package be determined based on the desired as fraction of as fraction of final MON. total fuel total fuel Ratios 0.0624 0.095 Toluene 0.03 * 0.429 0.2674 0.0407 pT 0.035 0.500 0.3120 0.0475 *** mT 0.005 0.071 0.0446 0.0068 ethanol 0 ** 0.000 0.0000 0.0000 Total 0.07 1.000 0.6240 0.0950 * more toluene may need to be added at refinery . . . depends on freeze point. ** ethanol would be added at refinery, blending stations, or depo (as it is not for car gas). *** these values for pT and mT would be about the same using either additive/blend package. But the ocean freight or other freight would be lower, as the low solvent concentrate would only require about rds the shipped volume.

[0069] In an embodiment, the concentrate will further include one or more alcohols. In an embodiment, the one or more alcohols will include C.sub.1 to C.sub.3 alcohols. In an embodiment, the alcohols will include ethanol. In an embodiment, the alcohols will consist essentially of ethanol. In an embodiment, the one or more alcohols will include methanol. In an embodiment, the one or more alcohols will include both ethanol and methanol. In an embodiment, the one or more alcohols will consist essentially of ethanol and methanol. In an embodiment, the concentrate will include ethanol in an amount that is from about 1:4 to about 2:3, by weight, compared to the amount of the p-toluidine present. In an embodiment, the concentrate will include methanol, and the amount of methanol is from about 1:4 to about 2:3, by weight, compared to the amount of the p-toluidine present.

[0070] In various embodiments, the weight ratio of aromatic solvent as compared to aromatic amine may be about 1:1, or more. In an embodiment, toluene comprises an amount that is from about 1:1 to about 2:1, by weight, compared to the amount of p-toluidine present. In an embodiment, the amount of aromatic amine may be at least thirty percent (30%) by weight of said concentrate. In an embodiment, the amount of alcohols may be about twenty percent (20%) or less by weight of the concentrate. A suitable additive package composition is provided in TABLE 3.

[0071] By use of the concentrate additive package just described above, a method for manufacturing a high octane unleaded aviation gasoline has been developed. The method includes (a) providing a concentrate additive package as set forth above, and (b) providing an unleaded aviation gasoline base fuel, as for example set forth in connection with Tests 1 through 20 above. More generally, in an embodiment, such an unleaded aviation gasoline base fuel, ready for blending, may include:

[0072] (i) a high grade aviation alkylate having a selected motor octane number (MON) of at least 96;

[0073] (ii) one or more dialkylbenzenes, the one or more dialkylbenzenes including one or more of meta-xylene, para-xylene, and ortho-xylene, wherein the meta-xylene and the para-xylene together comprise no more than about forty five percent (45%) by weight of a finished high octane unleaded aviation gasoline, and the para-xylene comprising no more than thirteen percent (13%) by weight of a finished high octane unleaded aviation gasoline, and the ortho-xylene comprising no more than eleven percent (11%) by weight of the finished high octane unleaded aviation gasoline;

[0074] (iii) two or more monoalkylated benzenes, the two or more monoalkylated benzenes including ethylbenzene and toluene; and

[0075] (iv) the combination of effective amounts of butane and isopentane wherein vapor pressure in said unleaded aviation gasoline is in the range between 38 kPa and 49kPa, as measured using ASTM Standard D5191.

[0076] The method further includes mixing the concentrate additive package with the unleaded aviation gasoline base fuel just described above. said unleaded aviation gasoline base. In an embodiment, the method includes adding an effective amount of the concentrate wherein the freezing point of said high octane unleaded aviation gasoline is minus forty seven degrees Centigrade (47 C.), or lower, as tested per ASTM standard D910 for Grade 100LL aviation gasoline. In an embodiment, the method includes adding an effective amount of the concentrate wherein the freezing point of said high octane unleaded aviation gasoline is minus fifty eight degrees Centigrade (58 C.), or lower, as tested per ASTM standard D910 for Grade 100LL aviation gasoline .

[0077] Further, concentrate additive packages may be provided which (a) include the alcohols as noted above, or (b) which do not include the alcohols as noted above. In the latter case, the method further includes providing selected additional alcohols, and mixing the same with the concentrate package, prior to admixture with the unleaded aviation gasoline base fuel, or alternatively directly mixing the additional alcohols directly into the unleaded aviation gasoline base fuel, or alternatively, providing the unleaded aviation base fuel with the selected additional alcohols already included. In any event, such selected additional alcohols may include ethanol and/or methanol. In an embodiment, isopropyl alcohol may be included.

[0078] Those of skill in the art will know that various products from refining operations may vary widely depending on the manufacturer. For example, refinery run iso-octane may vary in composition from refinery to refinery. Similarly, refinery run high grade aviation alkylates may vary in composition from refinery to refinery. And, producers of xylenes may have various end compositions in their output products, and other compounds may be found in such products, depending on equipment used for the production, and on the specifications of their various customers. However, one useful commercial xylol mixture useful for the manufacture of unleaded aviation gasoline blends have been found to include about twenty percent (20%) by weight of 1,4-dimethylbenzene, about fourteen percent (14%) of 1,2-dimethylbenzene, about forty four percent (44%) of 1,3-dimethylbenzene, and about twenty two percent (22%) of ethylbenzene. The reader is referred to the ASTM specification for the composition of an acceptable xylol mixture. However, it must be appreciated that other ranges of such xylol mixture components may be used to prepare novel unleaded aviation gasoline blends as described herein. And, other aliphatic aromatic hydrocarbons may be useful, with usage adjustable according to performance and economic objectives sought for a particular final unleaded aviation gasoline blend.

[0079] By way of background, it must be noted that in most circumstances, FBO Grade 100LL avgas typically has a MON in excess of the minimum MON required by the applicable ASTM Standard D910. Companies selling avgas typically include a small MON quality giveaway to assure that the avgas, at the pump, exceeds the minimum ASTM specifications. Thus, the MON of a FBO Grade 100LL may actually be found, upon sampling and testing, to be in the range of from about 100 to about 105, but more often in the middle of such range. However, the MON of a FBO Grade 100LL may be seen with values of 100, or 100.5, or 101, or 101.5, or 102, or 102.5, or 103, or more. Thus, economics may guide the final blend ratios utilized by a manufacturer of the unleaded aviation gasoline blends described herein in producing an unleaded aviation gasoline blend having a desired final MON, and a desired final supercharge rating. In other words, more or less of a selected monoalkylated benzene, dialkylated benzene may be used in manufacture of an unleaded aviation gasoline blend, depending upon the actual amount and composition of alklyated benzenes utilized, and which aromatic amine(s) are selected, such as m-toluidine, how much of the selected aromatic amines(s) are used, in the final unleaded aviation gasoline blend.

[0080] Various unleaded aviation gasoline base fuels may be suitable to provide the novel unleaded aviation gasoline blends and the accompanying results described herein. For example, a high grade aviation alkylate may be a useful base fuel, or a commercial grade iso-octane may be a useful base fuel. A mixture of a high grade aviation alkylate enhanced by addition of a portion of a commercial grade iso-octane may be a useful base fuel. As an example, an unleaded gasoline base fuel including (by weight) about twenty percent (20%) to about ninety percent (90%) of iso-octane, about one percent (1%) to about twenty percent (20%) of C.sub.4 to C.sub.5 paraffins, and the balance being primarily light alkylates, would be suitable. In an embodiment, providing iso-octane at about eighty percent (80%) may be suitable. In an embodiment, a paraffin composition in the ten percent (10%) to twenty percent (20%) range by weight, in the unleaded aviation base fuel, is anticipated to be suitable. In an embodiment, iso-pentane may be used as the paraffin of choice. In such case, iso-pentane in the unleaded aviation gasoline base fuel of about fifteen percent (15%) may be suitable. In various embodiments, it may be desirable to add butane and or iso-butane, to achieve distillation curve or vapor pressure objectives, to produce an exemplary unleaded aviation gasoline gasoline. To the extent feasible, consistent with my objective of teaching how to manufacture an ecomonical high octane unleaded aviation gasoline, it may in many cases be advantageous to use as much butane as feasible, compared to iso-pentane, consistent with compliance with applicable vapor pressure curve requirements.

[0081] Various unleaded aviation gasoline base fuels are available from various refineries, and in various embodiments of an unleaded aviation gasoline blend as taught herein, variations on the motor octane number (MON) of the aviation gasoline base fuels are anticipated to be workable. For example, in an embodiment, a 95 MON unleaded base fuel is known by my experiments to be workable, by blending an effective amount of 1,3-dimethylbenzene to the base fuel to provide an unleaded aviation gasoline blend meeting the performance objectives as set forth and claimed herein, which in an embodiment include detonation performance equivalent to, or better than, the full scale engine detonation performance of a Grade 100LL fuel that meets the minimum octane rating requirements set forth in ASTM Standard D910. And, in another embodiment, such objectives include detonation performance in a full scale engine equivalent to (FSEEMON), or better than, the full scale engine detonation performance of a selected FB Grade 100LL fuel having a selected MON. In an embodiment, addition of minor amount of aliphatic aromatic hydrocarbons may be provided, and such mixtures would preferably include such compounds as may enhance the octane performance of the final unleaded aviation gasoline fuel blend. Similarly, it is anticipated that use of a 94 MON base fuel will provide advantageous results, when used with somewhat increased proportions of 1,3-dimethylbenzene, and/or slightly increased proportions of a selected additional alkyl benzene or other aliphatic aromatic hydrocarbon, especially some of the above mentioned compounds that provide octane enhancing properties.

[0082] In the various examples just mentioned, where not otherwise already specified, methylbenzene (toluene) may be utilized as one of the one or more additional alkylated benzenes. Also, in the various examples just mentioned, where not otherwise already specified, where necessary or required for assuring adequate Reid Vapor Pressure of a final unleaded aviation gasoline fuel blend to meet applicable specifications or service conditions, a suitable unleaded aviation gasoline blend may further include more than zero percent (0%) up to about five percent (5%) butane, by weight.

[0083] In an embodiment, a selected butane, such as n-butane, may be added so that an unleaded aviation gasoline has a vapor pressure at 38 C., between a minimum of 38 kPa and a maximum of 49 kPa, per applicable ASTM test methods. Also, constituents such as iso-pentane or other paraffins may be provided. For example, as a supplement to amounts already in some unleaded aviation gasoline base fuels, amounts of more than zero percent (0%) up to about five percent (5%) of additional C.sub.5-C.sub.6 paraffins may be added. In an embodiment, because of its relatively low boiling point, iso-pentane may be selected for further addition to complete a workable, high performance, final unleaded aviation gasoline blend.

[0084] Availability of a novel unleaded aviation gasoline fuel blend having a functional performance as good or better than traditional aviation gasoline fuels with a motor octane number (MON) of 99.6, or more, which blend provides full scale aircraft piston engine detonation performance as good as, or better than, that currently available using Grade 100LL fuels which minimally meet the MON standards of ASTM Standard D910, will be of considerable interest to a large number of users of high performance aircraft piston engines. Moreover, availability of a novel unleaded aviation gasoline blend effective to increase the detonation performance of the unleaded aviation gasoline fuel blend to an equivalent (the FSEEMON of the unleaded aviation gasoline fuel blend), or better, when tested in a full scale aircraft engine, compared to the detonation performance of a selected FB Grade 100LL avgas having a selected MON, will be of even more interest to users of high performance aircraft piston engines. This is especially notable, since although various alkylbenzenes have long been utilized in various fuels, in so far as I am aware, mixtures using relatively high amounts of suitable octane enhancing alkylbenzenes, such as those described herein, have not been evaluated on full scale aircraft engines sufficiently to appreciate the FSEEMON advantage evident, compared to FBO Grade 100LL fuels of selected MON. The perceived general knowledge in the industry that unleaded fuels would underperform on full scale aircraft engines leaded fuels of the same or similar ASTM D2700 MON during detonation testing, based on lab testing, also led to the failure of others to fully investigate the detonation performance of unleaded fuels at actual engine operating conditions at moderate and heavy detonation intensity levels as determined by the ASTM D6424 algorithm .

[0085] In an embodiment, the high octane unleaded aviation gasoline fuel blends just described, and their use in the method of functional drop-in-substitution in an existing engine may include blends as set forth in any various samples with suitable freezing point conditions as noted in the Test examples above, or within the ranges set forth in the claims as regards compositions stated, with respect to various percentages of components, or with respect to the more specific formulations. As mentioned above, where necessary or required for assuring adequate Reid Vapor Pressure of a final unleaded aviation gasoline blend to meet applicable specifications or service conditions, unleaded aviation gasoline fuel blends having more than zero percent (0%) up to about five percent (5%) butane, by weight may be utilized. Also, for the same purpose, in addition to any iso-pentane or other paraffins that may be present in the aviation base fuel, using amounts of more than zero percent (0%) up to about five percent (5%) additional C.sub.5-C.sub.6 paraffins can be useful in practice of the method.

[0086] In an embodiment, a suitable aviation unleaded base fuel may be provided by a mixture of (a) iso-octane (at about seventy percent (70%) or more by weight) and (b) iso-pentane (at about twenty percent (20%) or less by weight). In an embodiment, a suitable commercial grade iso-octane may be provided having a MON of at least 97, per the ASTM D910 test procedure. In an embodiment, a suitable commercial grade iso-octane may be provided having a MON of at least 98, per the ASTM D910 test procedure. In an embodiment, a suitable commercial grade iso-octane may be provided having a MON of at least 99, per the ASTM D910 test procedure. In an embodiment, a suitable iso-octane may be provided using commercial grade 2,2,4 tri-methyl pentane.

[0087] Various unleaded aviation base fuels are described explicitly herein, or are incorporated herein by reference, and one or more of such base fuels may be used in preparation of a useful unleaded aviation gasoline blend according to the teachings herein.

[0088] In summary, various novel unleaded aviation gasoline blends have been described, as well as methods for their formulation, preparation, and manufacture. Testing has revealed that it is possible to provide blends of unleaded aviation gasolines, by combining high quality unleaded base fuels, such as high quality aviation alkylate or commercial iso-octane, with one or more di-alkylated an monoalkylated benzenes, and with suitable quantities of aromatic amines such as p-toluidine and/or m-toluidine, and selected amounts of alcohols, in order to formulate an exemplary finished high octane unleaded aviation gasoline. In various embodiments, such as finished high octane unleaded aviation gasoline exhibits, in full scale high performance aviation piston engines, detonation performance at least equivalent to that of a selected FBG Grade 100LL avgas having a selected MON. Those alkylated benzenes which provide octane enhancing properties to the unleaded aviation gasoline and which may be particularly useful in providing economic unleaded aviation gasoline fuel blends are, in an embodiment, those wherein the amount of commercially available di-alkylated benzenes, and particularly xylol mixtures including 1,3-dimethylbenzene, may be maximized in a novel high octane unleaded aviation gasoline blend.

[0089] In the foregoing description, for purposes of explanation, numerous details have been set forth in order to provide a thorough understanding of the disclosed exemplary embodiments for the formulation of unleaded aviation gasoline blends. For descriptive purposes, various relative terms may be used. Terms that are relative only to a point of reference are not meant to be interpreted as absolute limitations, but are instead included in the foregoing description to facilitate understanding of the various aspects of the disclosed embodiments. And, various actions or activities in a method described herein may have been described as multiple discrete activities, in turn, in a manner that is most helpful in understanding the developments described herein. However, the order of description should not be construed as to imply that such activities are necessarily order dependent. In particular, certain mixing or blending operations may not necessarily need to be performed in the order of presentation. And, in different embodiments, one or more activities may be performed simultaneously, rather than sequentially. Also, the reader will note that the phrase in an embodiment or in one embodiment has been used repeatedly. This phrase generally does not refer to the same embodiment; however, it may. Finally, the terms comprising, having and including should be considered synonymous, unless the context dictates otherwise.

[0090] Further, it should be understood by those of skill in the art and to whom this specification is directed that the term aircraft has been used herein consistent with US Federal Aviation Administration regulations to mean a device that is used or intended to be used for flight in the air. Under the same regulations and as used herein, the term rotorcraft means a heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors. Similarly, under the same regulations and as used herein, the term helicopter means a rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors. Finally, under the same regulations and as used herein, an aircraft engine means an engine that is used or is intended to be used for propelling aircraft. Appurtenances and accessories, and air compressors such as turbochargers, are normally considered by those of skill in the art, and under applicable FAA regulations, as components of the aircraft engines with respect to which they are operably connected. Thus, the unleaded aviation gasoline fuel blends described and claimed herein should be considered as useful for such piston driven aircraft engines.

[0091] Importantly, the aspects and embodiments described and claimed herein may be modified from those shown without materially departing from the novel teachings and advantages provided by the developments disclosed herein, and may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the embodiments presented herein are to be considered in all respects as illustrative and not restrictive or limiting. As such, this disclosure is intended to cover the formulations and blends described herein and the legal equivalents thereof. Numerous modifications and variations are possible in light of the above teachings. Therefore, the protection afforded should be limited only by the claims set forth herein, and the legal equivalents thereof.