Fuel Additives Useful for Reducing Particulate Emissions

Abstract

A fuel for use in a jet engine may be prepared by admixing a hydrocarbon fuel and a first additive selected from the group consisting of ethoxylated alkylphenol formaldehyde resins, maleic anhydride alpha olefin copolymers and mixtures thereof and a second additive comprising an admixture of platinum group and cerium compounds. The jet fuels including the additives may be used in jet engines where it is desirable to have reduced concentrations of particulates in exhausts, particularly when the jet engines are running at cruise speed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application 60/789,622 which was filed on Apr. 5, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel additives. The present invention particularly relates to fuel additives for use in jet engine fuel.

2. Background of the Art

Historically, hydrocarbon fuels, especially middle distillate fuels suitable for use in diesel or jet engines have been associated with pollution in the form of soot, smoke and particulate emissions in engine exhaust gases. Soot is the particulate matter resulting from heterogeneous combustion of hydrocarbon fuels, especially middle distillate fuels. Smoke can occur when soot is present in sufficient particle size and quantity, to be visible. Soot formation in engine exhaust gases is highly undesirable since it may cause environmental pollution, engine design limitations, increased engine maintenance and down-time and possible health problems for those who work around such engines.

The National Ambient Air Quality Standards established by the Clean Air Act requires the removal of fine particle concentrations from the atmosphere in an effort to decrease lung disease and related illnesses as well as mortality rates in urban areas. Currently, the standards have a criteria of PM10 (particles smaller than 10 microns in diameter, however, a standard for PM2.5 is in the process of being imposed.

Attempts have been made in the past to reduce emissions from the burning of fuels in internal combustion engines through the use of additives. For example, U.S. Pat. No. 3,817,720 relates to organic smoke suppressant additives and distillate hydrocarbon fuels containing the same. The preferred organic additive is an ether of hydroquinone. These compounds are ethers of phenolic-type compounds which contain two oxygen atoms attached to each phenyl moiety. Another hydrocarbon fuel additive, disclosed in U.S. Pat. No. 4,302,214, is a diether compound having low molecular weight. These compounds are described as suitable for increasing the octane number of gasoline. The suppression of particulate emissions from diesel engines is described in U.S. Pat. No. 4,240,802 which discloses the addition of a minor amount of a cyclopentadienyl manganese tricarbonyl and a lower alkyl or cycloalkyl nitrate to a hydrocarbon fuel.

The emissions from jet engines have also been a similar source of problems for both civilian and military aircraft. Such problems do not just occur with aircraft operation, but also with engine testing. The Clean Air Act also provides for the promulgation of national emission standards for engine test facilities including jet engine test cells. Efforts have been made to reduce emissions at such locations. For example, U.S. Pat. No. 6,237,395 discloses an annular after-reactor for use in the exhaust port of jet engine undergoing static test in order to reduce emissions.

It would be desirable in the art of preparing fuels for use in internal combustion engines such as jet and diesel engines to produce fuels that produce emissions within the national emission standards.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a jet fuel for use in jet engines comprising a hydrocarbon fuel and a first additive selected from the group consisting of ethoxylated alkylphenol formaldehyde resins, maleic anhydride alpha olefin copolymers and mixtures thereof, and a second additive comprising an admixture of platinum group and cerium compounds.

In another aspect, the invention is a process for preparing a jet fuel having reduced particulate emissions comprising admixing a jet fuel and a first additive selected from the group consisting of ethoxylated alkylphenol formaldehyde resins, maleic anhydride alpha olefin copolymers and mixtures thereof and a second additive comprising an admixture of platinum group and cerium compounds.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one aspect, the present invention is jet fuel including a first additive and a second additive to lower particulate emissions. For the purposes of this application, a jet fuel is an aviation fuel suitable for use in gas turbines and a jet engine is a gas turbine engine. Early gas turbine engines worked much like a rocket engine creating a hot exhaust gas which was passed through a nozzle to produce thrust. But unlike the rocket engine which must carry its oxygen for combustion, the turbine engine gets its oxygen from the surrounding air. Most modern, high speed passenger and military aircraft are powered by gas turbine engines.

Gas turbine engines come in a wide variety of shapes and sizes and can be found in many different types of aircraft besides high speed passenger and military jets. For example, gas turbines also are used to power some propeller driven aircraft such as helicopters and the C-130 cargo plane. They are also used in some land vehicles such as the main M1-A battle tank.

All gas turbine engines have some parts in common. One such part is an inlet wherein air enters the engine. The inlet also generally includes a fan which may function to feed air into the jet engine. The next part is a compressor where the air is compressed, usually by a series of blade impellers. After the compressor, a combustion chamber serves to admix the compressed air with fuel which is then ignited. The combustion products are then allowed to exit through the engine, turning a turbine as they expand. The turbine may then, in some applications, be used to power the rotors of a helicopter or drive the fan feeding air into the jet engine.

The jet fuel useful with the method of the present invention is any that can be used to fuel a jet engine. For example, in one embodiment, jet fuel may be a middle boiling distillate hydrocarbon, usually kerosene. In another embodiment, jet fuel may be a mixture of kerosene and gasoline and/or other light petroleum distillates. One example of jet fuel is a mixture of gasoline and kerosene or other light petroleum distillate in weight amounts of from 20:80 to 80:20. Jet fuel for civilian use is usually a kerosene type fuel and designated Jet A or Jet A1

In an alternative embodiment, the jet fuel useful with the method of the present invention may be a synthetic fuel. One embodiment of the present invention is a jet fuel having a very high flash point for use in applications where fire is a hazard such as onboard an aircraft carrier. Exemplary jet fuels for military use include those designated JP4 to 8:

JP4—wide cut, gasoline type fuel (according to U.S. Mil. Spec. (MIL-DTL-5624U));

JP5, a kerosene base fuel;

JP7, a high flash point special kerosene for advanced supersonic aircraft; and

JP8, a kerosene base fuel similar to Jet A1 (according to MIL-DTL-83133E).

Any jet fuel useful for fueling jet engines may be used with the method of the present invention.

The method of the present invention includes admixing jet fuel with a first additive useful for reducing particulate emissions. One family of compounds useful with the present invention as the first additive is ethylene oxide adducts of alkylphenol/formaldehyde resins. The alkylphenol/formaldehyde resins are prepared in a conventional manner, for example by reacting the formaldehyde with the alkylphenol in a ratio of from 2:1 to 1:2 under base or acid catalysis at from 80° to 250° C. with the aid of a high-boiling solvent for complete azeotropic removal of the resulting water of reaction. The alkylphenols used are, for example, nonylphenol, tert-butyl phenol or octylphenol. In general, an alkylsulfonic acid or alkylbenzenesulfonic acid, e.g. dodecylbenzenesulfonic acid, may be used as a catalyst.

In general, the alkylphenol/formaldehyde resin molecules contain from 4 to 12, preferably from 5 to 9, aromatic nuclei. These resins have active hydrogens which can form adducts with ethylene oxide. In one embodiment, ethoxylation is performed by reacting the resin with ethylene oxide using a basic catalyst, such as sodium or potassium hydroxide, at from 80° to 160° C. From about 5 to about 20 moles of ethylene oxide per mole of resin may be used. In one embodiment, from about 9 to about 15 moles are used. In still another embodiment, from 8 to 12 moles are used.

Examples of compounds of this type include a nonyl phenol formaldehyde resin ethoxylated with an average of about 9.5 moles of ethylene oxide per mole of resin, dodecyl phenol formaldehyde resin ethoxylated with about 12 moles of ethylene oxide per mole of resin, and diisoctylphenol formaldehyde resin ethoxylated with about 15 moles of ethylene oxide per mole of resin. These compounds may be prepared by any synthetic route known to those of ordinary skill in the art to be useful as long as they have the general structure described above.

Another family of compounds useful with the method of the present invention as the first additive includes copolymers of maleic anhydride with alpha olefins. The copolymer can be prepared by melt polymerization or bulk polymerization in the presence of a radical catalyst according to a conventional method. Examples of suitable alpha-olefins include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene. One or more of these alpha-olefins may be used. In one embodiment, the copolymer is prepared using C₄ to C₃₀ alpha olefins. In another embodiment, the copolymer is prepared using C₆ to C₂₈ alpha olefins. In still another embodiment, the copolymer is prepared using C₁₀ to C₂₆ alpha olefins. In still another embodiment, the copolymer is prepared using C₂₀ to C₂₄ alpha olefins.

The anhydride included in the alpha olefin maleic anhydride polymers is, in one embodiment, maleic anhydride. In other embodiments, other maleic anhydrides can be utilized. Exemplary of other maleic anhydrides are methylmaleic anhydride, dimethylmaleic anhydride, fluoromaleic anhydride, methylethyl maleic anhydride and the like. Accordingly, as employed herein the term “maleic anhydride” includes such anhydrides.

The alpha olefin maleic anhydride polymers may be prepared by any method known to those of ordinary skill in the art to be useful. Generally, the compounds are prepared by the free radical polymerization of C12-C30 alpha olefin and maleic anhydride, For example the olefin maleic anhydride polymers may be prepared by means of a number of conventional polymerization processes including polymerization processes as set forth in U.S. Reissue Pat. No. Re. 28,475 and U.S. Pat. Nos. 3,553,117, 3,560,455, 3,560,456, 3,560,457, 3,488,311, 4,522,992, 4,358,573, 4,871,823 and 4,859,752. These patents are all incorporated herein by reference.

The alpha olefin maleic anhydride polymers are generally low molecular weight materials having a number average molecular weight of from about 500 to about 50,000 daltons. In one embodiment the alpha olefin maleic anhydride polymers have a weight average molecular weight of from about 1,000 to about 15,000 daltons. In another embodiment, the alpha olefin maleic anhydride polymers have a weight average molecular weight of from about 3,000 to about 10,000 daltons.

The first additives may be used in a concentration ranging from about 10 ppm to about 10,000 ppm. In one embodiment, the first additive is used in a concentration of from about 100 to about 5,000 ppm. In another embodiment, the first additive is used in a concentration of from about 500 to 4,000 ppm. In still another embodiment, the first additive is used in a concentration of from about 1,000 to about 3,000 ppm. One embodiment employs the first additive at a concentration of about 2,000 ppm.

In the practice of the method of the present invention, a jet fuel is admixed with a second additive. One component of the second additive is a platinum group compound. Platinum group metals include platinum, palladium, rhodium, ruthenium, osmium, and iridium. Compounds including platinum, palladium, and rhodium, especially compounds of platinum alone or in combination with rhodium and/or palladium compounds can be desirable in some embodiments of the present invention.

The platinum group metal compositions can be of the type which are soluble in nonpolar hydrocarbon fuels, soluble in polar fuels such as those including methanol, ethanol, or other lower alkyl alcohols, or soluble in fuels having polar and nonpolar components such as emulsified fuels and gasohol. The platinum group metal compositions can be formulated according to the teachings below or as known to the art generally, to have the degree of stability necessary for the particular jet fuel with which it will be admixed.

In one embodiment, the platinum group metal compositions are those which are soluble in a nonpolar hydrocarbon fuel. Among these are hydrocarbon-fuel-soluble organometallic platinum group metal coordination compounds. The compounds in this group are any of those disclosed for example in U.S. Pat. Nos. 4,892,562 and 4,891,050 to Bowers and Sprague, 5,034,020 to Epperly and Sprague, 5,215,652 to Epperly, Sprague, Kelso and Bowers, and 5,266,083 to Peter-Hoblyn, Epperly, Kelso and Sprague, and WO 90/07561 to Epperly, Sprague, Kelso and Bowers, which references are incorporated herein by reference.

In another embodiment, the platinum group metal compositions are soaps, acetyl acetonates, alcoholates, diketonates, and sulfonates. Advantageously, in fuels or systems where water may be present, the platinum group metal composition will also be substantially insensitive to water, as evidenced by a partition ratio sufficient to maintain significant preferential solubility in the fuel. The relative solubility of the composition in the diesel fuel and water is important since there is often a substantial amount of water admixed in with fuel, and any platinum group metal composition which separates from the fuel can precipitate out or be lost as a coating on fuel system walls. The relative solubility of the composition in the fuel is referred to herein as the “partition ratio” and can be expressed as the ratio of the amount in milligrams per liter of composition which is present in the fuel to the amount which is present in the water. This can most easily be determined in a 100 milliliter (ml) sample which is 90% fuel and 10% water. By determining the amount of composition in the fuel and the amount in the water, the partition ratio can be readily determined.

The second component of the second additive of the method of the present invention is a cerium compound. Among specific cerium compounds useful with the method of the present invention are: cerium III acetylacetonate, and various cerium soaps such as cerium III naphthenate, cerium octoate, cerium stearate, cerium neodecanoate, and the like. Many cerium compounds are trivalent compounds meeting the formula: Ce(OOCR)₃, wherein R=hydrocarbon, preferably C₂ to C₂₂, and including aliphatic, alicyclic, aryl and alkylaryl.

The ratio of the two components of the second additive will be from 90:10 to 10:90. In one embodiment, the platinum group compound and the cerium compound will be present in equal (1:1) amounts. In another embodiment, the ratio will be from 20:80 to 80:20. In still another embodiment, the ratio will be from 30:70 to 70:30.

The second additive will be present in the jet fuel at a concentration of from about 10 ppm to 10,000 ppm. In one embodiment, the second component is present at a concentration of from 50 to 5000 ppm. In still another embodiment, the second component is preset at a concentration of about 100 ppm.

In the method of the present invention, a first additive and second additive is admixed with a jet fuel. These additives may be admixed with the jet fuel in any way known to be useful to those of ordinary skill in the art. These additives may be admixed with the jet fuel well in advance, immediately prior to use, or even in the fuel lines or the combustion chamber of the jet engine while the engine is in use. The two additives of the method of the present invention can be admixed with jet fuel together or separately. In one embodiment, the first and second additives are first admixed and then added to the jet fuel. In another embodiment, the first and second additives are not admixed but are added to the jet fuel at the same time and in the same way. In yet anther embodiment, the additives are admixed with the jet fuel at different times and in different ways.

EXAMPLES

The following examples are provided to illustrate the present invention. The examples are not intended to limit the scope of the present invention and they should not be so interpreted. Amounts are in weight parts or weight percentages unless otherwise indicated.

Example 1

A T-63 jet engine is used to test JP-8 including an additive mixture. The first component of the additive is an ethoxylated nonylphenol formaldehyde resin. The first component is added at the concentrations shown below in the Table. A second additive, which is a mixture of soluble cerium and platinum compounds, is used at a concentration of 100 ppm in the jet fuel.

The jet engine is fixed in place on a test stand. The engine is run at two speeds, idle and cruise. A base line is established for particle size and particle concentration by running the engine at both test conditions using untreated JP-8 fuel. Then the additives are admixed with the fuel and representative exhaust samples analyzed for particle size and concentration. The additives have essentially no effect on particle size at any concentration and either engine speed. The additives lower the concentration of particles per cm³ as shown below in the Table when used with the T-63 jet engine running at cruise speed.

Example 2

Example 1 is repeated substantially identically except that a maleic anhydride alpha olefin copolymer additive is used as the first additive. The first additive is a condensation of maleic anhydride and ethylene. The additives have essentially no effect on particle size at any concentration and either engine speed. The additives lower the concentration of particles per cm³ as shown below in the Table.

Comparative Example 3

Example 1 is repeated substantially identically except that a butylated reaction product of 2-p-cresol and dicyclopentadiene is used as the additive. The additive has essentially no effect on particle size or particle concentration at any use rate and either engine speed as shown below in the Table.

Brief Discussion of the Examples

Examples 1 and 2 show that both the ethoxylated alkylphenol formaldehyde resins and maleic anhydride alpha olefin copolymers additives of the present invention can be used in JP-8 fuel in conjunction with a platinum group and cerium additive to substantially reduce the number of particulates produced in T-63 jet engine at cruising speed. Comparative Example 3 shows that other compounds used as the additive do not have a similar effect.

TABLE
% Change From Baseline Concentration
at Cruise Speed Using a T-63 Jet Engine
		% Change Particle
	Additive Concentration	Concentration Relative
Additive Type	in JP-8	to Base Line
Ex 1	500	−24
Ex 1	1000	−41
Ex 1	2000	−38
Ex 2	500	−16
Ex 2	1000	−31
Ex 2	2000	−42
Ex 3*	500	+1
Ex 3*	1000	0
Ex 3*	2000	+2
*Comparative Example

Claims

1. A jet fuel for use in a jet engine comprising a hydrocarbon fuel and a first additive selected from the group consisting of ethoxylated alkylphenol formaldehyde resins, maleic anhydride alpha olefin copolymers and mixtures thereof and a second additive comprising an admixture of platinum group and cerium compounds.

2. The jet fuel of claim 1 wherein the first additive is an ethoxylated alkyl phenol formaldehyde resin.

3. The jet fuel of claim 2 wherein the ethoxylated alkyl phenol formaldehyde resin is prepared using an alkyl phenol that has an alkyl group having from about 6 to 12 carbon atoms in either a straight chain or branched chain configuration.

4. The jet fuel of claim 3 wherein the alkyl group is a nonyl group.

5. The jet fuel of claim 1 wherein the ethylene oxide is present in an amount of from 5 to 20 moles of ethylene oxide per mole of alkylphenol formaldehyde resin.

6. The jet fuel of claim 5 wherein the ethylene oxide is present in an amount of from 9 to 15 moles of ethylene oxide per mole of alkylphenol formaldehyde resin.

7. The jet fuel of claim 2 wherein the first additive is the reaction product of ethoxylating a nonylphenol formaldehyde resin with an average of about 9.5 moles of ethylene oxide per mole of resin.

8. The jet fuel of claim 2 wherein the first additive is the reaction product of ethoxylating a dodecylphenol formaldehyde resin with about 12 moles of ethylene oxide per mole of resin.

9. The jet fuel of claim 2 wherein the first additive is the reaction product of ethoxylating a diisoctylphenol formaldehyde resin with about 15 moles of ethylene oxide per mole of resin.

10. The jet fuel of claim 1 wherein the first additive is a copolymer of maleic anhydride with an alpha olefin.

11. The jet fuel of claim 10 wherein the alpha olefin is selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and mixtures thereof.

12. The jet fuel of claim 11 wherein alpha olefin is selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, and mixtures thereof.

13. The jet fuel of claim 12 wherein alpha olefin is selected from the group consisting of ethylene, propylene, and mixtures thereof.

14. The jet fuel of claim 10 wherein the maleic anhydride is substituted.

15. The jet fuel of claim 14 wherein the substituted maleic anhydride is selected from the group consisting of maleic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, fluoromaleic anhydride, methylethyl maleic anhydride, and mixtures thereof.

16. The jet fuel of claim 10 wherein the maleic anhydride is unsubstituted.

17. The jet fuel of claim 11 wherein the copolymer of maleic anhydride with an alpha olefin has a molecular weight of from about 500 to about 50,000 daltons.

18. The jet fuel of claim 17 wherein the copolymer of maleic anhydride with an alpha olefin has a molecular weight of from about 1000 to about 15,000 daltons.

19. The jet fuel of claim 18 wherein the copolymer of maleic anhydride with an alpha olefin has a molecular weight of from about 3000 to about 10,000 daltons.

20. The jet fuel of claim 1 wherein the first additive is present at a concentration of from about 10 to 10,000 ppm.

21. The jet fuel of claim 1 wherein the first additive is present at a concentration of from about 100 to 5,000 ppm.

22. The jet fuel of claim 1 wherein the first additive is present at a concentration of from about 1000 to 3,000 ppm.

23. The jet fuel of claim 1 wherein the second additive is an admixture of platinum and cerium compounds.

24. The jet fuel of claim 23 wherein the second additive is soluble in nonpolar fuels.

25. The jet fuel of claim 1 wherein the ratio of the two components of the second additive is from 90:10 to 10:90.

26. The jet fuel of claim 25 wherein the two components of the second additive is are present in equal (1:1) amounts.

27. The jet fuel of claim 1 wherein the second additive is present in the jet fuel at a concentration of from about 10 ppm to 10,000 ppm.

28. The jet fuel of claim 27 wherein the second additive is present in the jet fuel at a concentration of about 100 ppm.

29. A method for preparing a fuel for use in jet engines comprising admixing a hydrocarbon fuel and a first additive selected from the group consisting of ethoxylated alkylphenol formaldehyde resins, maleic anhydride alpha olefin copolymers and mixtures thereof and a second additive comprising an admixture of platinum group and cerium compounds.

30. The method of claim 29 wherein the first additive and second additive are admixed with the hydrocarbon fuel well in advance of its use.

31. The method of claim 29 wherein the first additive and second additive is admixed with the hydrocarbon fuel immediately prior to its use.

32. The method of claim 29 wherein the first additive and second additive are admixed with the hydrocarbon fuel in the fuel lines or the combustion chamber of the jet engine while the engine is in use.