US20100018112A1

US20100018112A1 - High octane unleaded fuel compositions and methods for increasing the maximum torque output value produced burning same

Info

Publication number: US20100018112A1
Application number: US12/180,845
Authority: US
Inventors: Joseph Michael Russo; Timothy Michael SHEA; Vinod Kumar NATARAJAN
Original assignee: Individual
Current assignee: Shell USA Inc
Priority date: 2008-07-28
Filing date: 2008-07-28
Publication date: 2010-01-28
Also published as: EP2324100A1; WO2010014501A1; CA2731955A1; AU2009276828A1

Abstract

An unleaded fuel composition comprising: about 45 volume % or more of one or more branched paraffins; about 34 volume % or less of one or more mono- and di-alkylated benzenes; from about 5 to about 6 volume % of one or more linear paraffins having from about 3 to 5 carbon atoms; and, one or more alkanol having from about 2 to 4 carbon atoms in an amount sufficient to boost the octane number of the unleaded fuel composition to 93 or greater, the unleaded fuel composition being free of any other ingredient or combination of ingredients that increases the octane number of the unleaded fuel composition by more than 1.0 unit.

Description

RELATED APPLICATIONS

The present application relates to U.S. patent application Ser. No. 11/609,742, filed Dec. 12, 2006, published as U.S. Publication No. 2008/0134571-A1 on Jun. 12, 2008, pending.

FIELD OF THE INVENTION

The present application relates to high octane unleaded fuel compositions. In one embodiment, the application relates to methods for increasing the maximum torque output value produced burning high octane unleaded fuel compositions.

BACKGROUND OF THE INVENTION

In the operation of spark-induced combustion engines, and particularly automotive engines operating on gasoline, the octane number of the fuel must be high enough to prevent knocking. Gasolines sold at service stations typically have an octane number of from about 87 to about 93. Fuels having such octane numbers are satisfactory for most automotive engines.
For high performance engines, and for racing engines in particular, fuels of even higher octane numbers are required. The lower the octane number, the more likely it is that knocking will occur. The production of fuels of progressively higher octane values is progressively more difficult to achieve. In particular, fuels having an octane value at or above 100 are highly desired and the most difficult to produce. This is particularly true for unleaded fuels. Unfortunately, commercially available unleaded fuels with an octane number of 93 or more tend to exhibit lower maximum torque output values and lower maximum power output values than may be desirable for high performance fuels.
A variety of components are blended to increase the octane value of unleaded fuels. Examples include aromatic amines, methyl ethyl tertiary butyl ether (MTBE), and/or increased aromatics.
For example, U.S. Pat. No. 4,812,146 to Jessup relates to fuels for high performance engines and for racing engines in particular. Jessup describes “a fuel composition . . . containing at least four components selected from the group consisting of butane, isopentane, toluene, MTBE, and alkylate, with alkylate being one such component and toluene another, said fuel having an octane value of about 100 or more.” Jessup, co. 1, 11. 34-39. Unfortunately, the use of MTBE (methyl tertiary butyl ether) raises concerns about air and drinking water quality. MTBE also has been banned from use in certain gasolines in California.
In Example III, Table 5, Jessup describes a fuel which does not comprise MTBE. However, the fuel comprises 60 vol. % toluene. The use of such a large amount of aromatic is undesirable. As Jessup explains, “higher levels of aromatics in the fuel may cause problems with elastomer components and/or drivability.” Jessup, col. 3, 11. 9-11.
A need exists for unleaded fuel compositions with high octane numbers that comprise less than 50 volume % aromatics and that produce high maximum torque output values, even in the absence of ethers, such as MTBE, or aromatic amines.

SUMMARY OF THE INVENTION

The present application provides unleaded fuel compositions having an octane number of greater than 93 that comprise less than 50 volume % aromatics and that produce high maximum torque output values, even in the absence of ethers or aromatic amines.
In one embodiment, the unleaded fuel compositions have an octane number of 95 or more.
In one embodiment, the unleaded fuel compositions have an octane number of 98 or more.
In one embodiment, the unleaded fuel compositions have an octane number of 99 or more.
In one embodiment, the unleaded fuel compositions have an octane number of 100 or more.
In one embodiment, the application provides an unleaded fuel composition comprising: about 45 volume % or more of one or more branched paraffins; about 34 volume % or less of one or more mono- and di-alkylated benzenes; from about 5 to about 6 volume % of one or more linear paraffins having from about 3 to 5 carbon atoms; and, one or more alkanol having from about 2 to 4 carbon atoms in an amount sufficient to boost the octane number of the unleaded fuel composition to 93 or greater, the unleaded fuel composition being free of any other ingredient or combination of ingredients that increases the octane number of the unleaded fuel composition by more than 1.0 unit.

DETAILED DESCRIPTION OF THE INVENTION

The present application provides unleaded fuel compositions having an octane number of greater than 93 that comprise less than 50 vol.% aromatics and that produce high maximum torque output values, even in the absence of ethers or aromatic amines. In one embodiment, the unleaded fuel compositions also produce a higher maximum power output value than observed burning commercially available unleaded racing fuels having an octane number of 93 or more.
The unleaded fuel compositions comprise one or more branched paraffins, one or more mono- and di-alkylated benzenes, one or more linear paraffins, and one or more alkanol. The unleaded fuel compositions are free of any other ingredient or combination of ingredients that increases the octane number of the unleaded fuel composition by more than 1.0 unit.
The octane number of a fuel composition generally is calculated as the sum of the Research Octane Number (RON) and the Motor Octane Number (MON) divided by 2, i.e., (R+M)/2. Unless otherwise indicated, the Research Octane Number (RON) is determined according to method ASTM D-2699-04a (2004) and the Motor Octane Number (MON) is determined according to method ASTM D-2700-04a (2004), both incorporated by reference.
The unleaded fuel compositions of the present application have octane numbers that are higher than those observed for most commercially available unleaded fuels. It is advantageous for the unleaded fuel composition to have an octane number sufficiently high to prevent the engine from knocking. In one embodiment, the unleaded fuel composition has an octane number of greater than 93. In one embodiment, the unleaded fuel composition has an octane number of 94 or more. In one embodiment, the unleaded fuel composition has an octane number of 95 or more. In one embodiment, the unleaded fuel composition has an octane number of 96 or more. In one embodiment, the unleaded fuel composition has an octane number of 97 or more. In one embodiment, the unleaded fuel composition has an octane number of 98 or more. In one embodiment, the unleaded fuel composition has an octane number of 99 or more. In one embodiment, the unleaded fuel composition has an octane number of about 100 or more.
In one embodiment, the unleaded fuel compositions unexpectedly produce higher maximum torque output values than commercially available unleaded fuels having an octane number of 93 or more. The maximum torque output value produced burning an unleaded fuel composition is important for vehicle acceleration. Maximum torque output values are even more important in high performance applications, such as racing applications. Specifically, the use of a fuel with a high maximum torque output value provides the driver with greater acceleration of a high performance vehicle. The maximum torque output value becomes particularly important at high speeds, such as those encountered in racing applications.
In one embodiment, the unleaded fuel compositions also produce a higher maximum power output value than commercially available unleaded fuels having an octane number of 93 or more.
In one embodiment, the blend produces a relatively smooth distillation curve. In one embodiment, burning the unleaded fuel composition in an engine produces a relatively smooth, even burn. In one embodiment, about 30 vol. % or less of the unleaded fuel composition volatilizes at or below about 93° C.(200° F.); about 50 volume % of the unleaded fuel composition volatilizes at a temperature of from about 93° C.(200° F.) to about 121° C.(250° F.); and, about 20 vol. % of the unleaded fuel composition volatilize at a temperature of greater than about 93° C.(200° F.)to about 149° C.(300° F.).

Composition of the Unleaded Fuel Compositions

In one embodiment, the application provides an unleaded fuel composition comprising: about 45 volume % of one or more branched paraffins; about 34 volume % or less of one or more mono- and di-alkylated benzenes; from about 5 to about 6 volume % of one or more linear paraffins having from about 3 to 5 carbon atoms; and, one or more alkanol having from about 2 to 4 carbon atoms in an amount sufficient to boost the octane number of the unleaded fuel composition to 93 or greater, the unleaded fuel composition being free of any other ingredient or combination of ingredients that increases the octane number of the fuel composition by more than 1.0 unit.

Branched Paraffin

In one embodiment, the blend comprises primarily one or more branched paraffins. In one embodiment, the blend comprises about 45 vol. % or more branched paraffins. In one embodiment, the blend comprises 46 vol. % or more branched paraffins. In one embodiment, the blend comprises 47 vol. % or more branched paraffins. In one embodiment, the blend comprises 48 vol. % or more branched paraffins. In one embodiment, the blend comprises 49 vol. % or more branched paraffins. In one embodiment, the blend comprises 50 vol. % or more branched paraffins. In one embodiment, the blend comprises 51 vol. % or more branched paraffins. In one embodiment, the blend comprises 52 vol. % or more branched paraffins. In one embodiment, the blend comprises 53 vol. % or more branched paraffins. In one embodiment, the blend comprises 54 vol. % or more branched paraffins. In one embodiment, the blend comprises 54 vol. % branched paraffins.

Linear Paraffins

In one embodiment, the unleaded fuel composition comprises one or more linear paraffins. In one embodiment, the one or more linear paraffins have from 3 to 5 carbon atoms. In one embodiment, the linear paraffins comprise butane. In one embodiment, the linear paraffin is butane.
In one embodiment, the unleaded fuel composition comprises about 5 vol. % or more of the linear paraffins. In one embodiment, the unleaded fuel composition comprises about 6 vol. % or less of the linear paraffins. In one embodiment, the unleaded fuel composition comprises about 5 vol. % of the linear paraffins. In one embodiment, the unleaded fuel composition comprises about 5 vol. % butane.

Alkylated Benzenes

In one embodiment, the blend comprises a quantity of alkylated benzenes. In one embodiment, the alkylated benzenes volatilize evenly along the distillation curve and increase the maximum power output value of the engine burning the unleaded fuel composition.
In one embodiment, the unleaded fuel composition comprises about 35 vol. % or less of one or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 34 vol. % or less of one or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 30 vol. % or less of one or more alkylated benzenes.
In one embodiment, the unleaded fuel composition comprises about 20 vol. % or more of one or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 22 vol. % or more of one or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 23 vol. % or more of one or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 24 vol. % or more of one or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 25 vol. % or more of one or more alkylated benzenes.
In one embodiment, the unleaded fuel composition comprises about 5 vol. % or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 8 vol. % or more alkylated benzenes. In one embodiment, the unleaded fuel composition comprises about 10 vol. % or more alkylated benzenes.
In yet another embodiment, the unleaded fuel composition comprises 25 vol. % of a combination of alkylated benzenes.
Suitable alkylated benzenes have the following general structure:
wherein R, R¹, and R²are selected from the group consisting of hydrogen and alkyl groups having from 1 to 4 carbon atoms, provided that at least one of R, R¹, and R²is an alkyl group. In one embodiment, R, R¹, and R²are selected from the group consisting of hydrogen and alkyl groups having from 1 to 2 carbon atoms. In one embodiment, R, R¹, and R²are selected from the group consisting of hydrogen and methyl groups. In one embodiment, the alkylated benzene is mono-alkylated benzene. In another embodiment, the alkylated benzene is a di-alkylated benzene. In another embodiment, the alkylated benzene is a tri-alkylated benzene. In one embodiment, one or more of R, R¹, and R²are methyl groups.
In one embodiment, the alkylated benzenes are a combination of one or more of mono-alkylated benzene, di-alkylated benzene, and tri-alkylated benzene.
In one embodiment, the unleaded fuel composition comprises a combination of di-alkylated benzene and mono-alkylated benzene. In one embodiment, the unleaded fuel composition comprises a combination of xylene and toluene.

Xylenes

In one embodiment, the unleaded fuel composition comprises xylenes. Xylenes are di-substituted benzenes having the following structure:
The CH₃substituents may be in a meta-, ortho-, or para-position.
In one embodiment, the unleaded fuel composition comprises p-xylene. P-xylene has the following structure:
In one embodiment, the unleaded fuel composition comprises about 10 vol. % or more xylenes. In one embodiment, the unleaded fuel composition comprises about 11 vol. % or more xylenes. In one embodiment, the unleaded fuel composition comprises about 12 vol. % or more xylenes. In one embodiment, the unleaded fuel composition comprises about 13 vol. % or more xylenes. In one embodiment, the unleaded fuel composition comprises about 14 vol. % or more xylenes. In one embodiment, the unleaded fuel composition comprises about 15 vol. % or more xylenes.
In one embodiment, the unleaded fuel composition comprises about 29 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 25 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 20 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 19 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 18 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 17 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 16 vol. % or less xylenes. In one embodiment, the unleaded fuel composition comprises about 15 vol. % or less xylenes.
In one embodiment, the unleaded fuel composition comprises about 15 vol. % p-xylene.

Toluene

In one embodiment, the unleaded fuel composition comprises toluene. Toluene is a mono-substituted benzene having the following structure:
In one embodiment, the unleaded fuel composition comprises about 5 vol. % or more toluene. In one embodiment, the unleaded fuel composition comprises about 6 vol. % or more toluene. In one embodiment, the unleaded fuel composition comprises about 7 vol. % or more toluene. In one embodiment, the unleaded fuel composition comprises about 8 vol. % or more toluene. In one embodiment, the unleaded fuel composition comprises about 9 vol. % or more toluene. In one embodiment, the unleaded fuel composition comprises about 10 vol. % or less toluene. In one embodiment, the unleaded fuel composition comprises 10 vol. % toluene.
In one embodiment, the unleaded fuel composition comprises a combination of xylene and toluene. In one embodiment, the unleaded fuel composition comprises a combination of p-xylene and toluene.
In one embodiment, the unleaded fuel composition comprises a combination of about 15 vol. % xylene and about 10 vol. % toluene. In one embodiment, the unleaded fuel composition comprises a combination of about 15 vol. % p-xylene and about 10 vol. % toluene.

Alkylate

In one embodiment, the blend comprises an amount of alkylate. In one embodiment, the alkylate is effective to stabilize the distillation curve of the blend along its length. In one embodiment, the alkylate assists the blend in burning evenly in the engine.
The term “alkylate” typically refers to branched-chain paraffin. The branched-chain paraffin typically is derived from the reaction of isoparaffin with olefin. Alkylation is described, for example, in J. Gary, et al. Petroleum Refining, Technology and Economics (2d Ed. 1984) Chapter 10, pp. 159-183, and in Kirk Othmer. Concise Encyclopedia of Chemical Technology (4^thEd. 1999) Vol. 1, p. 75-76. Both of the cited portions of the foregoing references are hereby incorporated by reference.
Various grades of branched chain isoparaffins and mixtures are commercially available. The grade typically is identified by the range of the number of carbon atoms per molecule, the average molecular weight of the molecules, and/or the boiling point range of the alkylate. As used herein, the word “alkylate” refers to hydrocarbon compositions used for fuel applications comprising 90 volume % or more isoparaffins, as measured according to ASTM D5134-98 (2003), incorporated herein by reference. In one embodiment, the alkylate also meets one or more of the following parameters, as measured according to ASTM D5134-98 (2003): comprises less than 2 volume % paraffins; comprises less than 1 volume % olefins; comprises less than 5 volume % naphthenes; comprises less than 3 volume % aromatics; comprises less than 0.3 volume % molecules with 14 or more carbon atoms; has an initial boiling point of about 96° C.; and, has a final boiling point of about 394° C. In one embodiment, the alkylate has an API gravity of about 690 API, as measured according to ASTM D4052(IP365)-96 (1996). In one embodiment, the alkylate has a dry vapor pressure of from about 27.6 kPa (4 psi) to about 35 kPa (5 psi), as measured according to ASTM D5191-EPA-07 (2007). In one embodiment, the alkylate is a refinery grade alkylate formed by the reaction of isobutene with 1-butene in the presence of a strongly acidic catalyst.
Suitable alkylate typically has a RON of, for example, from about 93 to about 95. Suitable alkylate typically has a MON of, for example, from about 91 to about 92. Suitable alkylate typically has an octane number (R+M/2) of, for example, from about 92 to about 93.5.
Suitable alkylates can be obtained from a variety of sources, including Solvents & Chemicals, Pearland, Tex.; Equistar Chemicals; Texas Petrochemicals; Shell Chemical Company; and, various refineries.
In one embodiment, the unleaded fuel composition comprises about 50 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 51 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 52 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 53 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 54 vol. % or more alkylate. In yet another embodiment, the unleaded fuel composition comprises about 55 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 56 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 57 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 58 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 59 vol. % or more alkylate. In one embodiment, the unleaded fuel composition comprises about 60 vol. % or less alkylate.

Alkanol

In one embodiment, the unleaded fuel composition comprises alkanol. In one embodiment the alkanol has from 2 to 4 carbon atoms. In one embodiment, the alkanol is ethanol.
In one embodiment, the blend comprises a sufficient amount of alkanol to boost the octane number of the unleaded fuel composition to the desired level. In one embodiment, the unleaded fuel composition comprises about 3 vol. % or more alkanol. In one embodiment, the unleaded fuel composition comprises about 4 vol. % or more alkanol. In one embodiment, the unleaded fuel composition comprises about 5 vol. % or more alkanol. In one embodiment, the unleaded fuel composition comprises about 6 vol. % or less alkanol. Specific Formulations
In one embodiment, the unleaded fuel composition comprises 6 volume % butane; 50 volume % alkylate; 5 volume % toluene, 29 volume % p-xylene; and, 10 volume % ethanol. In one embodiment, the unleaded fuel composition comprises 5 volume % butane; 60 volume % alkylate; 10 volume % toluene, 15 volume % p-xylene; and, 10 volume % ethanol.

Other Components

The unleaded fuel composition optionally may comprise a variety of other components as long as they do not increase the octane number by more than about 1.0 unit.
Suitable components include, for example, fuel additives as listed in ASTM D-4814-04 (2004), incorporated herein by reference, or as specified by a regulatory body, e.g., U.S. California Air Resources Board (CARB) or the U.S. Environmental Protection Agency (EPA).
The unleaded fuel composition may comprise one or more oxygenate octane boosters. Suitable oxygenate octane boosters include, for example, alkyl ethers.
In one embodiment, the unleaded fuel composition comprises alkyl ether comprising an alkyl group having from 1 to 6 carbon atoms. In one embodiment, the alkyl group has from 3 to 6 carbon atoms. In one embodiment, the alkyl group is a branched chain alkyl group having from 3 to 6 carbon atoms. In one embodiment, the alkyl group is a tertiary alkyl group having from 4 to 6 carbon atoms. Suitable tertiary alkyl groups include, for example, tert-butyl groups and tert-amyl groups.
In one embodiment, the alkyl ether is dialkyl ether. In one embodiment, the alkyl ether is asymmetric dialkyl ether. In one embodiment, the dialkyl ether comprises a first tertiary alkyl group and a second alkyl group having from 1 to 6 carbon atoms. In one embodiment, the dialkyl ether comprises a first tertiary alkyi group and second alkyl group having from 1 to 3 carbon atoms. In one embodiment, the second alkyl group is a linear alkyl group. In one embodiment, the second alkyl group is selected from the group consisting of a methyl group and an ethyl group. Specific examples of suitable alkyl ethers include methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether, and methyl tertiary amyl ether.
Suitable oxygenate octane boosters are made using known processes and are available commercially from a variety of sources.
In one embodiment, the unleaded fuel composition comprises corrosion inhibitor. Suitable corrosion inhibitors include, for example, carboxylic acids, esters, alkanolamides, amines, etc.
The unleaded fuel composition also may comprise other additives or components. Examples of other components suitable for use in the unleaded fuel composition include other paraffins, aromatic hydrocarbons, alcohols, ethers, and/or esters. Refinery streams that may be used in the unleaded fuel include, for example, distillation products and reaction products from a refinery such as catalytic reformate, heavy catalytic cracked spirit, light catalytic cracked spirit, straight run gasoline, isomerate, light reformate, light hydrocrackate, and naphtha. Other gasoline components include olefins (in particular with one double bond per molecule). Examples include liquid alkene having from 5 to 10 carbon atoms. In one embodiment, the liquid alkene has from 6 to 8 carbon atoms. The liquid alkene may be linear or branched. Specific examples of suitable liquid alkenes include pentene, isopentene, hexene, isohexene, heptene, and mixtures thereof.
Examples of other paraffins that may be used in the unleaded fuel include cyclic paraffins. In one embodiment, the unleaded fuel composition comprises naphtha. Where the unleaded fuel composition comprises naphtha, the unleaded fuel composition comprises less than 17.9 weight percent naphtha. In one embodiment, the unleaded fuel composition comprises less than 15 weight percent naphtha. In one embodiment, the unleaded fuel composition comprises less than 10 weight percent naphtha. In one embodiment, the unleaded fuel composition comprises less than 5 weight percent naphtha. In one embodiment, the unleaded fuel composition comprises less than 2 weight percent naphtha. In one embodiment, the unleaded fuel composition comprises less than 1 weight percent naphtha. In one embodiment, the unleaded fuel composition does not comprise naphtha.
The fuel also may contain lead replacement additives and/or other common additives which have no significant impact on octane value, for example, dyes, deicing agents, agents for preventing exhaust valve seat wear, anti-oxidants, corrosion inhibitors, anti-static additives, detergents and the like.
The unleaded fuel composition may not comprise any additive. The unleaded fuel composition also may comprise one or more fuel additives. Where used, the unleaded fuel composition typically comprises about 1000 ppm or less total amount of additives. Where one or more additives are present, each additive typically is present in an amount of about 0.1 ppm or more. In one embodiment, each additive is present in an amount of about 0.5 ppm or more. In one embodiment, each additive is present in an amount of about 1 ppm or more. In one embodiment, each additive is present in an amount of 100 ppm or less. In one embodiment, each additive is present in an amount of 50 ppm or less. In one embodiment, each additive is present in an amount of 20 ppm or less.
In one embodiment, the unleaded fuel composition comprises lead replacement additive. In one embodiment, the unleaded fuel composition comprises antioxidant. In one embodiment, the unleaded fuel composition comprises detergent additive. In one embodiment, the unleaded fuel composition comprises a combination of lead replacement additive, antioxidant, and detergent additive.
Where used, the unleaded fuel composition typically comprises, for example, about 20 mg/kg or more lead replacement additive. In one embodiment, the unleaded fuel composition comprises from about 25 mg/kg or more lead replacement additive. In one embodiment, the unleaded fuel composition comprises about 30 mg/kg or more lead replacement additive. In one embodiment, the unleaded fuel composition comprises about 60 mg/kg or less lead replacement additive. In one embodiment, the unleaded fuel composition comprises about 55 mg/kg or less lead replacement additive. In one embodiment, the unleaded fuel composition comprises about 50 mg/kg or less lead replacement additive.
Where used, the unleaded fuel composition typically comprises, for example, about 10 mg/kg or more antioxidant. In one embodiment, the unleaded fuel composition comprises about 15 mg/kg or more antioxidant. In one embodiment, the unleaded fuel composition comprises about 20 mg/kg or more antioxidant. In one embodiment, the unleaded fuel composition comprises about 50 mg/kg or less antioxidant. In one embodiment, the unleaded fuel composition comprises about 45 mg/kg or less antioxidant. In one embodiment, the unleaded fuel composition comprises about 40 mg/kg or less antioxidant.
Where used, the unleaded fuel composition typically comprises, for example, about 0.01 g/liter (0.05 g/gallon or 3.8 liter) or more detergent additive. In one embodiment, the unleaded fuel composition comprises about 0.02 g/liter (0.08 g/gallon, or 3.8 liter) or more detergent additive. In one embodiment, the unleaded fuel composition comprises about 0.03 g/liter (0.1 g/gallon) or more detergent additive. In one embodiment, the unleaded fuel composition comprises about 1 g/liter (4 g/gallon) or less detergent additive. In one embodiment, the unleaded fuel composition comprises about 0.9 g/liter (3.5 g/gallon) or less detergent additive. In one embodiment, the unleaded fuel composition comprises about 0.8 g/liter (3 g/gallon) or less detergent additive. Suitable detergent additives include, for example, polyisobutylene amines, polyisobutylene Mannich reaction products, polyether amines, and combinations thereof.
In one embodiment, the unleaded fuel composition comprises: about 40 mg/kg lead replacement additive; about 30 mg/kg antioxidant; and, from about 0.3 g/liter (1 g/gallon) to about 0.5 g/liter (2 g/gallon) detergent additive.
Specific examples of suitable blends are given in the following examples, which are illustrative only and should not be construed as limiting the claims:

COMPARATIVE EXAMPLE 1

U.S. Pat. No. 4,812,146 to Jessup relates to fuels for high performance engines and for racing engines in particular. Jessup describes “a fuel composition . . . containing at least four components selected from the group consisting of butane, isopentane, toluene, MTBE, and alkylate, with alkylate being one such component and toluene another, said fuel having an octane value of about 100 or more.” Jessup, co. 1, 11. 34-39.
Unfortunately, MTBE (methyl tertiary butyl ether) raises concerns about air and drinking water quality. MTBE also has been banned from use in certain gasolines in California.
In Example III, Table 5, Jessup describes a fuel which does not comprise MTBE,. However, the fuel comprises 60 vol. % toluene. The use of such a large amount of aromatic is undesirable. As Jessup explains, “higher levels of aromatics in the fuel may cause problems with elastomer components and/or drivability.” Jessup, col. 3, 11. 9-11.

COMPARATIVE EXAMPLE 2

U.S. Pat. No. 6,353,143 to Fang, et al (“Fang”) describes a fuel composition which may comprise base fuels including “isoparaffins, branched paraffins, aromatic hydrocarbons, and mixtures thereof . . . in the amount of 50% to about 100%.” Fang, col. 1, 11. 37-41. Fang states that “[preferably, the octane number of the fuel compositions is greater than about 70, more preferably, the octane number of the fuel composition is greater than about 81.” Fang, col. 2, 11. 1-3.
Fang reports the octane number of a number of commercially available branched paraffins in Table 2. Fang, col. 6, 11. 14-33. The highest of the reported octane numbers is 90.5 [(86.1+94.9)/2] for Isopar H, which is available from Exxon Chemical. Id., and Fang, col. 3, lines 36-47. The highest reported octane number in Fang's Examples is 90.5. Fang, Example 6, col. 7, 11. 44-50.

EXPERIMENTAL EXAMPLES

A number of blends were tested to identify unleaded fuel compositions having octane numbers of 93 or more, preferably 100 or more. All of the blends tested in the following examples fell within the following compositional ranges:

Experimental Blends


	Component	Vol. %

	Butane	5-6
	Toluene	5-10
	Alkylate	50-60
	p-Xylene	15-29
	Ethanol	10

The alkylate used in the blends had the composition given in the following Table. The numbers in the following Table represent the normalized volume %, based on the total volume of the composition, pursuant to the referenced ASTM test methods. The referenced ASTM methods are incorporated herein by reference:


Method	Test	Results	Units

ASTM D4052	API Gravity	69.1	°API
(IP365) - 96 (1996)
ASTM D5191-EPA-07	Dry Vapor Pressure	32.6 (4.73)	Kpa (Psi)
(2007)	Equivalent
	Sample	Normal
ASTM D6730-06	Paraffins	1.78	Vol. %
(2006)
	Iso-Paraffins	90.08	Vol. %
	Olefins	0.17	Vol. %
	Naphthenes	4.16	Vol. %
	Aromatics	2.69	Vol. %
	C14+	0.26	Vol. %
	Unknown	0.86	Vol. %
ASTM D86-07 (2007)	Initial Boiling	35.6 (96.1)	° C. (° F.)
	Point
	5% Evaporated	71.6 (160.9)	° C. (° F.)
	10% Evaporated	86.8 (188.2)	° C. (° F.)
	20% Evaporated	91.7 (197.0)	° C. (° F.)
	30% Evaporated	100.2 (212.3)	° C. (° F.)
	40% Evaporated	104.4 (219.9)	° C. (° F.)
	50% Evaporated	108 (226.4)	° C. (° F.)
	60% Evaporated	109.4 (229.0)	° C. (° F.)
	70% Evaporated	112.6 (234.7)	° C. (° F.)
	80% Evaporated	118.9 (246.0)	° C. (° F.)
	90% Evaporated	135.9 (276.6)	° C. (° F.)
	95% Evaporated	172.7 (341.9)	° C. (° F.)
	Final Boiling Point	201 (393.8)	° C. (° F.)
	% Recovered	95.9	Vol. %
	% Residue	1.5	Vol. %
	% Loss	2.6	Vol. %
	E200	21.3	Vol. %
	E300	92.2	Vol. %

The alkylate comprised greater than 90 vol. % isoparaffins.

EXPERIMENTAL EXAMPLE 1

The following experimental blends were prepared and tested for octane number:


	Blend 1	Blend 2
	Vol. %	Vol. %

Butane	6	5
Alkylate	50	60
Toluene	5	10
p-Xylene	29	15
Ethanol	10	10
Total	100	100

The RON, MON, and octane number [R+M)/2] were measured according to ASTM D-2699-04a (RON) and ASTM D-2700-04a (MON) (2004). For Blend 1, the RON was 104, the MON was 94.8, and the octane number was 100. For Blend 2, the RON was 104, the MON was 94.8 and the octane number was 100.

EXPERIMENTAL EXAMPLE 2

In this Example, Blend 1, Blend 2, and three leading commercial unleaded fuels having octane numbers of 100 or more were distilled. The three commercial unleaded fuels are designated Comparative Fuel 1 (CF-1), Comparative Fuel 2 (CF-2), and Comparative Fuel 3 (CF-3).
FIG. 1 shows the comparative distillation curves for the fuels, from an initial boiling point (IBP) through a final boiling point (FBP). CF-1 exhibited a much higher IBP, and very little of the components in CF-1 volatilized at temperatures lower than about 91° C. (195° F.).
In FIG. 2, the distillation curve for CF-1 was removed. As seen from FIG. 2, the distillation curves for CF-2 and CF-3 are similar. The amount of CF-2 that volatilized from about 66° C.(150° F.) to about 93° C. (200° F.) and from about 98.9° C.(210° F.) to about 121° C. (250° F.) was less than the amounts of CF-3 volatilized at the same temperatures.
From a temperature of above about 115.5° C.(240° F.) to about 135° C.(275° F.), much of Blend 1 volatilized. The amount of Blend 1 that volatilized over a temperature of 121° C.(250° F.) increased rapidly with increased temperature, becoming similar to Blend 2 over a temperature of about 135° C.(275° F.). FIG. 3 is an enlarged view of the portion of FIG. 2 from T50 to FBP, or from about 107° C.(225° F.) to about 149° C.(300° F.).

EXAMPLE 3

Blends 1 and 2 were tested using a GM 6.6L Race dynamometer to compare the maximum torque output value and the maximum power output value compared to two leading unleaded fuels in the U.S. market stated to have an octane number of 93. Two additional commercial fuels were tested in this example, Comparative Fuel 4 (CF-4) and Comparative Fuel 5 (CF-5). The following were the results:


	Max Torque	Max Power
Fuel	Output Value	Output Value

Blend

1	360.5	364.4
	Blend 2	366.3	366.8
	CF-4	361	366.3
	CF-5	358.8	364.9

FIG. 5 is a graph of the foregoing results. As seen from the foregoing and from FIG. 5, Blend 1 exhibited a higher maximum torque output value and a higher maximum power output value than either Blend 2 or the two commercial fuels. Blend 2 exhibited a higher maximum torque output value than CF-5, but otherwise exhibited either an equal or a slightly lower maximum torque output value and maximum power output value compared to the two commercial fuels.
The experimental fuel clearly generated the highest maximum torque output value of all of the fuels tested. Although the increase was less significant, the experimental fuel also generated the highest maximum power output value of all of the fuels.
Persons of ordinary skill in the art will recognize that many modifications may be made to the foregoing description. The embodiments described herein are meant to be illustrative only and should not be taken as limiting the invention, which will be defined in the claims.

Claims

1. An unleaded fuel composition comprising:

about 45 volume % or more of one or more branched paraffins;

about 34 volume % or less of one or more mono- and di-alkylated benzenes;

from about 5 to about 6 volume % of one or more linear paraffins having from about 3 to 5 carbon atoms; and,

one or more alkanol having from about 2 to 4 carbon atoms in an amount sufficient to boost the octane number of the unleaded fuel composition to 93 or greater, the unleaded fuel composition being free of any other ingredient or combination of ingredients that increases the octane number of the unleaded fuel composition by more than 1.0 unit.

2. The unleaded fuel composition of claim 1 comprising about 10 volume % of the one or more alkanol.

3. The unleaded fuel composition of claim 1 comprising about 54 volume % branched paraffins.

4. The unleaded fuel composition of claim 1 wherein:

about 40 vol. % of the blend volatilizes at temperatures of from about 38° C.(100° F.) to about 105° C.(220° F.);

about 50 volume % of the blend volatilizes at temperatures of from about 105° C.(220° F.) to about 121° C.(250° F.);

about 10 vol. % of the blend volatilizes at from about 121° C.(250° F.) to about 149° C.(300° F.).

5. The unleaded fuel composition of claim 1 having an octane number of 95 or more.

6. The unleaded fuel composition of claim 1 having an octane number of 100 or more.

7. The unleaded fuel composition of claim 1 wherein the one or more oxygenate is ethanol.

8. The unleaded fuel composition of claim 6 wherein the one or more oxygenate is ethanol.

9. The unleaded fuel composition of claim 1 wherein the one or more mono- and di-alkylated benzenes comprise a first amount of toluene and a greater amount of p-xylene.

10. The unleaded fuel composition of claim 7 wherein the one or more mono- and di-alkylated benzenes comprise a first amount of toluene and a greater amount of p-xylene.

11. The unleaded fuel composition of claim 8 wherein the one or more mono- and di-alkylated benzenes comprise a first amount of toluene and a greater amount of p-xylene.

12. The unleaded fuel composition of claim 9 comprising:

from about 5 vol. % to about 10 vol. % toluene; and, from about 15 to about 29 vol. % p-xylene.

13. The unleaded fuel composition of claim 11 comprising:

14. The unleaded fuel composition of claim 1 wherein the one or more linear paraffins having from about 3 to 5 carbon atoms is butane.

15. An unleaded fuel composition comprising:

about 10 volume % toluene;

about 15 volume % p-xylene;

about 54 volume % branched paraffins;

about 5 volume % butane; and,

about 10 volume % ethanol.

16. A method for increasing the maximum torque output value produced by an engine burning an unleaded fuel composition, the method comprising burning the unleaded fuel composition of claim 1 in the engine.

17. A method for increasing the maximum torque output value produced by an engine burning an unleaded fuel composition, the method comprising burning the unleaded fuel composition of claim 14 in the engine.

18. A method for increasing the maximum power output value produced by an engine burning an unleaded fuel composition, the method comprising burning the unleaded fuel composition of any of claim 1 in the engine.

19. A method for increasing the maximum power output value generated by an engine burning an unleaded fuel composition, the method comprising burning the unleaded fuel composition of claim 14 in the engine.

20. The method of claim 16 further comprising producing a maximum torque output value of greater than 361.

21. The method of claim 16 further comprising producing a maximum torque output value of 366 or more.

22. The method of claim 18 further comprising producing a maximum power output value of 366 standard horsepower or more.

23. The method of claim 21 further comprising producing a maximum power output value of 366 standard horsepower or more.