Automotive gasoline fuel for internal combustion engine

Abstract

A fast burning, gasoline type composition for spark ignited internal combustion engines having a ASTM D-86, 90% distillation temperature of 310° F. or less and an octane number (R+M)/2 of 82 or less that can be used with a reduced spark advance in the engines to effect a reduction in NOx exhaust emissions. Also disclosed is a gasoline having low octane (82-87) which can be used interchangeably in engines having a reduced spark advance and in engines having conventional spark advance.

Description

FIELD OF THE INVENTION

[0001] The present invention pertains to gasoline compositions and the use thereof in spark ignited, internal combustion engines as in automobile type engines.

BACKGROUND INFORMATION

[0002] Pollutants produced by combustion include oxides of nitrogen which are more commonly referred to as NOx (where x is an integer which represents the number of oxygen atoms in the molecule). Such oxides include NO and NO2. In the combustion process NOx is formed by air (a gas containing nitrogen and oxygen) being subjected to high temperatures for a period of time. Recent studies have been made on lower 90% distillation temperature gasoline which show that faster burning gasoline (lower 90% distillation temperature) comes up to high temperature more rapidly increasing the time the nitrogen and oxygen in the air are exposed to high temperature thereby causing an increase in NOx (see the figure). This type of fuel is described in U.S. Pat. No. 5,015,356 which is incorporated herein by reference.

[0003] Gasolines now used as fuel in current spark ignited internal combustion engines require octane numbers (R+M)/2 falling almost entirely within the range of 84-94. Some engines require a higher octane gasoline than others depending on their compression ratio or carbon deposit buildup (age) in order to avoid or reduce engine “knock” or to improve fuel combustion efficiency.

[0004] Lower octane gasolines have been used in the past in low compression engines but were abandoned in common practice because of poor efficiency and power output. It was later discovered that increasing the engine compression and advancing the spark timing substantially improved the fuel combustion efficiency. Achieving this result. however, required that the gasoline have a much higher octane number. In fact, the state of California now requires by law that automotive type gasoline made, imported, sold or used in California must have a minimum octane number (R+M)/2 of 87. It would be highly desirable if lower octane gasolines could be efficiently used in currently available engines especially if their use resulted in reduction of NOx pollution.

[0005] As described below. the present invention relates in part to a low octane fuel having an octane rating of less than 82 and an ASTM D-86 90% distillation temperature less than 310° F. (referred to herein as E-gasoline II). The aforementioned E-gasoline II is advantageous because it is a fuel with a low octane rating which can nonetheless be used in conventional internal combustion automobile engines by merely retarding the spark advance of the engine. Thus current engines are able to provide improved combustion efficiency with gasoline having octane numbers less than 82 providing the spark advance is retarded and the gasoline has a low distillation temperature (ASTM D-86 90% distillation temperature less than 310° F.).

[0006] Using prior art gasoline in engines that have a retarded spark advance causes an increase in pollutants of combustion so that prior art gasoline and the E-gasoline II cannot be used interchangeably in an engine having less spark advance. Accordingly, it would be highly desirable to additionally provide a gasoline which can be efficiently used in current engines without retarding the spark advance as well as in engines in which the spark advance has been retarded to accommodate the E-gasoline II.

SUMMARY OF THE INVENTION

[0007] An objective of this invention is to provide a novel gasoline for use in a spark ignited internal combustion engine that will permit or allow reduction of NOx emissions.

[0008] It is an objective of this invention to provide a low octane (less than 87) automotive gasoline which can nonetheless be used to efficiently operate conventional automotive engines without producing undesirable levels of pollution. More particularly, it is a first objective of this invention to provide a method for achieving NOx reduction by engine modification so that the fuel of this invention can be efficiently used. In this regard it has been discovered that the fuels of this invention which have an octane number less than 82 and a 90% distillation temperature of 310° F. or less can nonetheless be used in conventional internal combustion automobile engines by merely reducing the spark advance of the engine. Such gasoline (referred to herein as E-gasoline II) cannot be used in conventional engines in which the spark advance has not been retarded. Thus, a second objective of the invention is to provide low octane fuels (referred to herein as E-gasoline III) which can be used interchangeably in engines with conventional spark advance as well as in engines in which the spark advance has been retarded to accommodate the E-gasoline II.

[0009] It is a further objective of this invention to provide a fuel that is clean burning and which produces low levels of pollutants in the exhaust stream of an internal combustion engine.

[0010] It is a further objective of this invention to provide a gasoline having good driveability and cold start properties.

[0011] It is a still further object of this invention to provide a gasoline that will perform well at air to fuel ratios above stoichiometric in an internal combustion engine.

[0012] It is yet another object of this invention to provide a liquid fuel that can be formed into a vapor or gaseous state and yet will tend to remain in this state when mixed with induction air in an internal combustion engine.

[0013] These and other objects are obtained with a gasoline that has a low 90% distillation temperature and a low octane number. The low 90% distillation temperature is used so that the gasoline can burn quickly and more thoroughly when mixed with air and ignited in an engine. The low octane number is utilized so that the combustion rate with air is rapid. The octane number may be lowered by known techniques such as by reducing the amount of high octane components used in the production of the gasoline or by reducing the octane booster additives which are conventionally added to gasoline. The desired distillation temperature can be achieved by conventional gasoline production or refining techniques such as by distilling the heavy ends off of gasoline blending streams in a refinery. More particularly, the first and other objectives (i.e., the objectives associated with the E-gasoline II) are achieved by providing a gasoline having an octane number less than 82 and an ASTM D-86 90% distillation temperature of 310° F. or less. The second and other objectives (objectives associated with E-gasoline III) are achieved by providing a gasoline having an octane number which at the high end is less than 87 and at the low end is 82 (i.e., from 82 up to but not including 87) and an ASTM D-86 90% distillation temperature of 310° F. or less (preferably less than 290° F.).

[0014] A common technical feature shared by all the fuels of this invention is that they all have an octane number less than 87 and a low 90% distillation temperature.

BRIEF DESCRIPTION OF THE DRAWING

[0015] The figure is a graph which shows the effects on auto exhaust emissions when the ASTM D-86 90% distillation temperature is reduced from 360° F. to 280° F.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

[0016] 1) E-Gasoline II

[0017] Lower endpoint gasoline reduces “cylinder wall wetting”, thus permitting less “knocking” in an engine at octane levels less than the minimum established by the state and federal regulators for modern, Phase 2 gasoline-87 octane minimum. All of the octane numbers indicated herein are determined from the formula (R+M)/2 where R is defined by ASTM D-2699 and M is defined by ASTM D-2700. Through testing and using standard federal test procedures, it has been discovered that such lower endpoint gasoline can be used to operate a standard automobile engine without knocking even though the gasoline has an octane number (R+M)/2 less than 82 (e.g., as low as 81.8). An example of such a fuel with a 90% distillation temperature of less than 310° F. is the “special” gasoline of Example 1. Example 1 shows a comparison between conventional gasoline and a gasoline of the present invention (designated herein as “SPECIAL”) having an ASTM D-86 90% distillation temperature of less than 310° F.

[0018] Previously low octane gasolines were used for low compression engines. However, it was discovered that by lowering the 90% distillation temperature (as determined by ASTM D-86 distillation tests) to 310° F. or less, (preferably within a range of 252°-282° F.) the octane number of currently available gasoline could also be lowered and used in today's engines which now require gasolines having an octane number of 84 or higher. The fuels of this invention have octane ratings of less than 82, most preferably less than 80.

[0019] In engine dynamometer testing (example 2) it was further discovered that lower 90% distillation temperature gasoline could operate a standard automobile engine at less spark advance than would be required for the same engine burning conventional 87 octane gasoline. Furthermore, it was also discovered that burning low 90% distillation temperature gasoline in the engine with less spark advance achieved reduced emissions, particularly reduced emissions of NOx. This is very important in that lower 90% distillation temperature gasolines normally increase NOx emissions (see the figure) but by reducing spark advance these same fuels can operate at reduced levels of NOx emissions (see example 2). Lowering spark advance also permits a further reduction in octane number (R+M)/2 to less than 81.8, preferably to 80 or less.

[0020] The gasoline of this invention uses standard gasoline components which may include additives and/or oxygenates. Thus, apart from the lower 90% distillation temperature and lower octane, the gasoline of the present invention is otherwise the same as conventional gasoline which is currently available.

[0021] In a preferred embodiment the ASTM D-86 90% distillation temperature falls within the range of 265° F. to 285° F. In addition, the octane number of the gasoline is preferably in the range of 72-82. Such a gasoline can lower the pollutants in the exhaust of a conventional internal combustion engine by retarding the spark advance of the vehicle preferably within a 4° to 12° range.

[0022] The present invention is unique in that the novel low octane gasoline described herein is workable in currently available engines and also provides improved combustion efficiency and lower levels of combustion pollutants compared to the use of currently available gasolines in these engines. Also the gasolines of this invention are easy to vaporize or gasify and once in the vapor or gaseous state they have improved stability so that they essentially remain in this state when combined with induction air. This characteristic improves the gas-to-air ratio and the ignition properties of higher air-to-fuel ratio combustion charges. The low octane of the gasoline also contributes to higher air-to-fuel ratio combustion since excess air is an excellent octane booster. If octane values get too high, the fuel will not have time to burn completely in the engine. It is well known that fuel combustion efficiency and lower tailpipe pollutants are achieved with air-to-fuel ratios higher than stoichiometric.

[0023] In a preferred embodiment the gasoline has a distillation (ASTM D-86) endpoint temperature less than 345° F. and an octane number (R+M)/2 less than 80. The fuel may additionally contain additives, oxygenates, fuel extenders or other compositions which enhance the properties or combustion characteristics of gasoline. Such additives may be used singularly or in any combination thereof.

[0024] In operation the fuels of this invention may be used in an internal combustion engine in the form of a liquid, vapor or gaseous state, or in any combination thereof. The use of the fuel of this invention results in a reduction of harmful emissions of combustion from internal combustion engines.

[0025] The gasoline of this invention also allows one to achieve reliable ignition of combustion mixtures containing higher air-to-fuel ratios than are currently used in spark ignited internal combustion engines.

[0026] 2) E-Gasoline III

[0027] Except as noted below, the above description of the E-gasoline II also applies to the gasolines of the present invention which can be used interchangeably in engines having conventional spark advance and in engines with retarded spark advance (E-gasoline III). The E-gasoline III differs from E-gasoline II by requiring a particular combination of 90% distillation temperature (as determined by ASTM D-86) and octane number so that it can be used interchangeably in conventional engines with retarded spark advance and conventional engines with conventional spark advance.

[0028] It has been discovered that by lowering the 90% distillation temperature (as determined by ASTM D-86) to 310° F. or less (preferably less than 290° F.) the octane number of prior art gasoline could also be lowered and used in today's engines which now require gasoline having an octane number of 87 or higher. In this embodiment of the invention the gasoline has an octane rating which ranges from 82 up to but not including 87. Preferably the octane rating is 82-84.

[0029] In a preferred embodiment the ASTM D-86 90% distillation temperature is less than 290° F. In addition, in this preferred embodiment the octane number of the gasoline is in the 82-84 range.

[0030] The E-gasoline III is unique in that it is a low octane gasoline which is workable in currently available engines with or without spark advance retardation and also provides improved combustion efficiency and lower levels of combustion pollutants compared to the use of prior art gasolines in these engines.

[0031] In another embodiment the E-gasoline III has a true boiling point distillation endpoint temperature less than 345° F. and an octane number (R+M)/2 less than 84 (i.e., 82 up to but not including 84).

EXAMPLE 1

[0032] Dynamic testing done at Compliance and Research Services, Inc., Linden, N.J., on an Oldsmobile Cutlass in November, 1989 shows that a fuel designed for improved injector volatilization (i.e., the fuel of this invention having a 90% distillation temp less than 310° F. designated herein as SPECIAL) can perform well without engine knock at low octane. Both HC (hydrocarbon) and CO emissions increase substantially when “knocking” occurs in an engine. In this test the fuel of the invention performed well without elevated emissions of HC and CO, thus establishing that the engine performed well without knocking even though the fuel utilized had an octane rating of only 81.8. 1 GASOLINE* SPECIAL** Emissions HC (avg) - .146 HC (avg) - .136 City CO (avg) - 1.449 CO (avg) - 1.431 Emissions HC (avg) - .076 HC (avg) - .070 Highway CO (avg) - .785 CO (avg) - .593 *Octane R + M/2 = 92.0 **Octane R + M/2 = 81.8 Emissions data in grams per mile.

EXAMPLE 2

[0033] At Pittsburgh Applied Research Center (PARC) tests were done using a Pontiac 4-cylinder engine (2.5 L) with a Go Power Dynamometer and a TEC Electromotive Control System. The following data were taken from spread sheets operating the engine at about 2,000 rpm with all conditions being about the same except for hydrocarbons. NOx and fuel used as per the following chart: 2 SPARK ADVANCE DATE HC NOx (measured in degrees) GASOLINE Jun. 14, 1990 784 1,076 49 Chevron Jun. 14, 1990 788 1,232 49 Chevron Jun. 13, 1990 800 960 49 Special* Jun. 13, 1990 804 968 49 Special* Jun. 13, 1990 752 556 43 Special* Jun. 13, 1990 744 596 44 Special* Jun. 13, 1990 712 368 38 Special* Jun. 13, 1990 712 328 38 Special* *less than 310 degrees F., 90% distillation temperature. Note the change in NOx with the variation in spark advance.

[0034] While the present invention has been described in terms of certain preferred embodiments and exemplified with respect thereto, one skilled in the art will readily appreciate that variations, modifications, changes, omissions and substitutions may be made without departing from the spirit thereof It is intended, therefore, that the present invention be limited solely by the scope of the following claims:

Claims

1. A gasoline composition for use as a fuel in a spark ignited internal combustion engine. said fuel comprising a hydrocarbon mixture with the proviso that said gasoline has an ASTM D-86 90% distillation temperature of 310° F. or less and an octane number (R+M)/2 which is less than 82.

2. The fuel of claim 1 having an octane value which is 80 or less.

3. The fuel of claim 1 wherein the 90% distillation temperature is in the range of 265° F.-285° F. and the octane number falls within a 72-82 range.

4. A method of operating a spark ignited internal combustion engine having at least one combustion chamber therein and a spark advance setting; said method comprising introducing gasoline and air into said at least one combustion chamber and igniting said mixture with a spark; said gasoline comprising a hydrocarbon mixture with the proviso that said gasoline has an ASTM D-86 90% distillation temperature of 310° F. or less and an octane number (R+M)/2 which is less than 82; with the proviso that said spark advance setting of said engine is set at level whereby knocking is avoided while said engine is running.

5. The method of claim 4 wherein said gasoline has an octane number which is 80 or less.

6. The method of claim 4 wherein the gasoline has an ASTM D-86 90% distillation temperature in the range of 265° F.-285° F. and the octane number (R+M)/2 falls within the 72-82 range.

7. A method for reducing NOx emissions from a spark ignited internal combustion engine having at least one combustion chamber therein and a spark advance setting which is set at a minimum effective amount to avoid engine knocking when gasoline having an octane rating of at least 82 is used as a fuel to run said engine; wherein the improvement comprises using gasoline of the invention as the fuel in the operation of the engine with the proviso that the spark advance is retarded an effective amount to avoid engine knocking; said gasoline comprising a hydrocarbon mixture having an ASTM D-86 90% distillation temperature of 310° F. or less and an octane number (R+M)/2 which is less than 82.

8. The method of claim 7 wherein the gasoline has an octane number which is 80 or less.

9. The method of claim 7 wherein the gasoline has an ASTM D 86 90% distillation temperature in the range of 265° F.-285° F. and an octane number (R+M)/2 falling within a 72-82 range.

10. A gasoline fuel composition for use in a spark ignited, internal combustion engine, said fuel comprising a hydrocarbon mixture with the proviso that said mixture has an ASTM D 86 endpoint temperature less than 345° F. and an octane number (R+M)/2 less than 80 and where said composition may include additives and fuel extenders common to gasoline.

11. A gasoline composition for use as a fuel in a spark ignited internal combustion engine. said gasoline comprising a hydrocarbon mixture with the proviso that said gasoline has an ASTM D-86 90% distillation temperature of 310° F. or less and an octane number (R+M)/2 falling in the range of 82 up to but not including 87.

12. The gasoline of claim 1 wherein the 90% distillation temperature is less than 290° F.

13. A gasoline composition for use as a fuel in an internal combustion engine, said gasoline comprising a hydrocarbon mixture having a true boiling point endpoint distillation temperature of 345° F. or less and an octane number (R+M)/2 falling within the range of 82 up to but not including 87.

14. A method of operating an internal combustion engine having at least one combustion chamber therein; said method comprising introducing gasoline and air into said at least one combustion chamber and igniting said mixture with a spark; said gasoline comprising a hydrocarbon mixture with the proviso that said gasoline has an ASTM D-86 90% distillation temperature of 310° F. or less and an octane number (R+M)/2 falling in the range of 82 up to, but not including, 87.

15. The method of claim 14 wherein said gasoline has a 90% distillation temperature which is less than 290° F.

16. The method of claim 14 wherein said gasoline comprises a hydrocarbon mixture having a true boiling point endpoint distillation temperature of 345° F. or less and an octane number (R+M)/2 falling within a range of 82 up to. but not including, 87.

17. The method of claim 14 wherein said engine is operated with an air-to-fuel ratio which is in excess of stoichiometric.

18. The method of claim 15 wherein said engine is operated with an air-to-fuel ratio which is in excess of stoichiometric.

19. The method of claim 16 wherein said engine is operated with an air-to-fuel ratio which is in excess of stoichiometric.

20. A method for reducing tailpipe emissions of pollutants in automobiles which comprises using the gasoline of claims 11, 12, or 13 to run automobiles powered by internal combustion engines.

21. The method of claim 20 wherein said gasoline includes additives, oxygenates or any gasoline volume extender.

22. A method for reducing NOx emissions from a spark ignited internal combustion engine having at least one combustion chamber therein and a spark advance setting; said method comprising introducing gasoline and air into said at least one combustion chamber and igniting said mixture with a spark; said gasoline being the gasoline of claims 1, 2 or 3; with the proviso that said spark advance setting of said engine is set at a level whereby knocking is avoided while said engine is running.

23. A method for reducing combustion pollutants from a spark ignited internal combustion engine which comprises operating said engine above stoichiometric air-to-fuel ratios with the gasoline of claims 11, 12 or 13.