EP1425366A2

EP1425366A2 - Strained ring compounds as combustion improvers for normally liquid fuels

Info

Publication number: EP1425366A2
Application number: EP02797796A
Authority: EP
Inventors: Mark R. Baker; Daniel T. Daly
Original assignee: Lubrizol Corp
Current assignee: Lubrizol Corp
Priority date: 2001-09-05
Filing date: 2002-08-29
Publication date: 2004-06-09
Also published as: AU2002332746A1; WO2003020852A3; US20040244277A1; WO2003020852A2

Abstract

Fuel compositions comprising a major amount of a normally liquid hydrocarbon based fuel and a minor amount of a compound having at least one strained ring group containing from 3 to 4 ring atoms.

Description

TITLE: STRAINED RING COMPOUNDS AS COMBUSTION IMPROVERS FOR NORMALLY LIQUID FUELS

FIELD OF THE INVENTION

This invention relates to combustion improving additives for normally liquid fuels. In particular, the combustion improvers are strained ring compounds.

BACKGROUND OF THE INVENTION The industry has continued to search for ways to improve combustion of normally liquid fuels. These include fuels used in heating systems, internal combustion engines and the like. Government agencies have imposed regulations requiring continuing reduction of emissions resulting from the combustion of fuels. Improved fuel economy is also required, not only by government regulations but also by consumers facing increased costs for fuels. Improved combustion of fuels generally results in a reduction in harmful emissions and more efficient utilization of fuels resulting in greater fuel economy.

Combustion improvers of this invention improve combustion characteristics of fuels. The improved combustion characteristics include reduced particulate emissions, reduced CO emissions, reduced NO_x emissions, reduced hydrocarbon emissions, greater power output, reduced misfiring and improved fuel efficiency.

U.S. Patent 4,670,131 relates to fouling of equipment used for processing of organic feed streams containing olefinic compounds controlled by inhibiting polymerization of the olefinic compounds by carrying out the processing in the presence of from about 20 ppb to less than 1,000 ppb of a stable free radical, such as nitroxide.

U.S. Patent 5,460,634 describes an additive package comprising an oil- soluble, stable free radical, such as a nitroxide, or a precursor therefor, used in a fuel oil to reduce, on combustion of the fuel oil, one or more of particulate emissions, hydrocarbon emissions, carbon monoxide emissions, and oxides of nitrogen emissions.

U.S. Patent 5,525,127 relates to hydrocarbonaceous distillate fuel compositions and additive concentrates are described as providing improved performance in evaporative burners. The additive components comprise a mixture formed that at least (a) a cyclopentadienyl manganese tricarbonyl compound; (b) a succinic derivative ashless dispersant; (c) an aliphatic dicarboxylic acid having at least 24 carbon atoms in the molecule, the two carboxyl groups being separated from each other by at least 6 carbon atoms; and (d) a metal deactivator of the chelation type. Preferably, the compositions also contain (e) alkoxylated alkylphenol; (f) a demulsifying agent; (g) a tertiary monoamine in which each substituent on the nitrogen atom is a hydrocarbyl group; and (h) liquid inert solvent having a final boiling point no higher than approximately 600°C. The compositions are devoid of any metal-containing additive component other than the cyclopentadienyl manganese tricarbonyl compound.

U.S. Patent 5,529,706 describes tolyltriazole derived esters of tri, tetra, and poly carboxylic acids or an acid generating compound which are effective lubricity additives for lube oils, greases, or distillate fuels. U.S. Patent 5,578,556 relates to triazole-dialkyl maleate derivatives which are described as effective metal passivators and antiwear additives for lubricants and fuels.

U.S. Patent 5,591,237 describes a fuel additive concentrate package comprising a detergent/dispersant, an organic nitrate combustion improver, and a corrosion inhibitor comprising dimer and/or trimer acid to provide enhanced shelf life stability by treating the concentrate with a shelf life stability amount, for example 1,500 and 10,000 ppm, respectively of acid selected from the group consisting of nitric acid/hydrochloric acid.

U.S. Patent 5,669,938 describes a fuel composition which comprises a water- in-oil emulsion comprising a major proportion of a hydrocarbonaceous middle distillate fuel and about 1 to about 40 volume percent water, and an emission reducing amount of at least one fuel-soluble organic nitrate ignition improver such as 2-ethylhexyl nitrate providing reduction of exhaust emissions from diesel engines.

U.S. Patent 5,782,937 relates to fuel compositions containing hydrocarbon fuels in the gasoline boiling range and organic nitrogen-containing compounds selected from organic nitrates and/or organic nitro compounds. The fuel compositions exhibit improved ignition properties, including reduced emissions and reduced misfires.

U.S. Patent 5,944,858 relates to hydrocarbonaceous fuels and additive compositions therefor which comprise: a) one or more fuel-soluble manganese carbon yl compounds; and b) one or more fuel soluble alkali or alkaline earth metal containing neutral or basic detergent salts and preferably, also contain c) one or more of fuel-soluble ashless dispersants; d) at least one fuel soluble demulsifying agent; e) at least one aliphatic or cycloaliphatic amine; and f) at least one metal deactivator. The fuel compositions are said to possess improved combustion characteristics.

U.S. Patent 5,928,392 describes a burner operated by continuously feeding into its combustion zone while combustion is occurring therein, (a) a middle distillate burner fuel with which has been blended a minor combustion improving amount of manganese polycarbonyl compound and a total amount of air above 100% of the stoichiometric amount required for complete combustion of all fuel being introduced into said zone but which is below 105% of such stoichiometric amount. Preferably, alkali or alkaline earth metal containing detergent and fuel soluble dispersant have been blended into the fuel.

European Patent EP 0420581A1 describes an additive for hydrocarbon fuels which includes ethanolamine nitrate as an additive to reduce the quantity of smoke and improve the efficiency of combustion. Fuels are improved by the addition of the additive, which can be prepared by the reaction of ammonium nitrate and anhydrous ethanol in the presence of one or more nitro compounds of formula

where R is a hydrogen atom or a C_1-4 alkyl radical, at a temperature of not more than 40-45°C, the nitro derivative being applied in a concentration of 1 to 3% by weight, the molar ratio between the nitro compound(s) and the ammonium nitrate being at least 0.05:1. PCT Patent Publication WO 00/105740 describes an emulsified water- blended fuel composition comprising: (A) a hydrocarbon boiling in the gasoline or diesel range; (B) water; (C) a minor emulsifying amount of at least one fuel-soluble salt made by reacting (C)(1) at least one acylating agent having about 16 to 500 carbon atoms with (C)(II) ammonia and/or at least one amine; and (D) about 0.001 to about 15% by weight of the water-blended fuel composition of a water-soluble, ashless, halogen-, boron-, and phosphorus-free amine salt, distinct from component (C). In one embodiment, the composition further comprises (E) at least one co- surfactant distinct from component (C); in one embodiment, (F) at least one organic cetane improver; and in one embodiment, (G) at least one antifreeze.

Several means are available for reducing emissions, extending hydrocarbon based, especially hydrocarbon, fuels or both. These include, for example, addition of oxygenates to the fuel or incorporating therein significant amounts of water, usually as an emulsion. Since oxygenates typically have reduced fuel value compared to purely hydrocarbon fuels, and, of course, water has no fuel value, the use thereof will often result in a noticeable loss of 'driveability', i.e., performance. It is desirable to find additive systems that provide combustion improvement to a wide variety of normally liquid fuels, and particularly to fuels containing oxygenates or water. The instant invention addresses this need. The combustion improvers of this invention are also useful to improve performance of poor driveability fuels. SUMMARY OF THE INVENTION

The instant invention is directed to fuel compositions comprising a major amount of a normally liquid hydrocarbon based fuel and a minor amount of a compound having at least one strained ring group containing from 3 to 5 ring atoms. The strained ring group containing compound provides improved combustion properties to a wide variety of normally liquid hydrocarbon based fuels, including fuels such as hydrocarbon fuels, biomass fuels, oxygenates and water-containing emulsified fuels. The invention also is directed to a method for improving the combustion characteristics of a normally liquid hydrocarbon based fuel comprising incorporating therein a combustion improving amount of a compound having at least one strained ring group containing from 3 to 4 ring atoms. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the terms "hydrocarbyl" or "hydrocarbon based" mean that the group being described has predominantly hydrocarbon character within the context of this invention. These include groups that are purely hydrocarbon in nature, that is, they contain only carbon and hydrogen. They may also include groups containing substituents or atoms which do not alter the predominantly hydrocarbon character of the group. Such substituents may include halo-, alkoxy-, nitro-, hydroxyl, etc. These groups also may contain hetero atoms. Suitable hetero atoms will be apparent to those skilled in the art and include, for example, sulfur, nitrogen and oxygen. Therefore, while remaining predominantly hydrocarbon in character within the context of this invention, these groups may contain atoms other than carbon present in a chain or ring otherwise composed of carbon atoms.

In general, no more than about three non-hydrocarbon substituents or hetero atoms, and preferably no more than one, will be present for every 10 carbon atoms in the hydrocarbon or hydrocarbon based groups. Most preferably, the groups are purely hydrocarbon in nature, that is they are essentially free of atoms other than carbon and hydrogen.

It must be noted that as used in this specification and in the appended claims, the singular forms also include the plural unless the context clearly dictates otherwise. Thus the singular forms "a", "an", and "the" include the plural; for example "an amine" includes mixtures of amines of the same type. As another example the singular form "amine" is intended to include both singular and plural unless the context clearly indicates otherwise.

The expression 'substantially free of as used herein means that the referred to material is entirely absent or present in an amount so small as to be undetectable using ordinary means or is present in no more than an impurity amount. Compounds Containing Strained Ring Groups

The fuel compositions of this invention comprise at least one compound having at least one strained ring group containing from 3 to 4 ring atoms. The compounds can be monocyclic or polycyclic compounds, having fused ring systems and/or ring systems connected directly or via a bridge group, and/or spiro- compounds which polycyclic compounds have, for example, from two to four rings and which are unsubstituted or substituted and can contain heteroatoms such as, for example, O or N (preferably not N) in one or more rings and/or can contain fused thereto aromatic or heteroaromatic rings. The individual strained cyclic rings contain from 3 to 4, more often 3, ring members. These include cyclopropyl groups, cyclobutyl groups and cyclopentyl groups as well as oxygen-containing analogues thereof.

As defined herein, 'strained ring' compounds include 3 and 4 membered rings containing olefinic unsaturation, but do not include olefinically unsaturated 5- membered rings. Preferably, the strained ring compounds used in this invention are substantially saturated and most preferably are free of olefinic unsaturation. 'Substantially saturated' means no more than 5% of the strained ring compounds contain ring unsaturated bonds. The expression 'free of olefinic unsaturation' means the strained ring compounds contain no more than an impurity amount of unsaturated ring components. In one embodiment, the ring group is a hydrocarbyl group substantially free of heteroatoms. Examples include cyclopropyl methanol, cyclobutyl amine, bicyclopropyl, and cyclobutyl hydroxylamine.

In another embodiment, the ring contains one or more heteroatoms as mentioned hereinabove. Such heteroatom containing compounds may be illustrated by, for example, furans, dioxolanes, oxetanes, epoxides, aziridines, and thio- analogues thereof and compounds containing one or more of these groups.

Heterocyclic ring groups contain at least 2 carbon atoms and preferably no more than 2 heteroatoms, often but one heteroatom, and preferably only oxygen heteroatom or no heteroatoms at all. Preferred heteroatoms are oxygen and nitrogen, although compounds containing sulfur heteroatoms are also useful. Examples of preferred oxygen containing compounds or groups are dioxolane, epoxide, oxetane and furan. Specific examples include 3,3-dimethyloxetane, l-methoxy-2-methylpropylene oxide, 2- methoxydioxolane and 2,5-dimethoxytetrahydrofuran, preferably, 3,3- dimethyloxetane or bicyclopropyl. As noted hereinabove, the compound may contain more than one strained ring group, which groups may be present as fused, linked, spiro- etc groups. Preferably, such compounds contain 2 strained ring groups.

In one preferred embodiment, the compounds containing two or more strained ring groups are substantially free of heteroatoms. Examples include dicyclopropyl ketone, dicyclobutyl ketone and compounds of the formula

and

The strained ring group containing compound is typically used in amounts ranging from about 50 to about 50,000 parts by weight per million parts by weight (ppm) of fuel, more often from about 500 to about 20,000 ppm, typically about 5,000 ppm and in another embodiment, about 2500 ppm.

In one embodiment, the fuel compositions of this invention further comprise supplemental additives which serve to enhance to the performance of the fuel compositions of this invention. In one embodiment, the fuel compositions further comprise a hydroxylamine having the general formula

wherein each of R_a and R_b is, independently, a member selected from the group consisting of H, a primary hydrocarbyl group and a secondary hydrocarbyl group, particularly, H or a hydrocarbyl group containing from 1 to about 25 carbon atoms, and especially a lower alkyl group, provided that neither of R_a nor R_b is a strained ring group, and n ranges from 1 to about 30, preferably, from 1 to about 4, and most preferably, 1. Of course, it is obvious that when R_a is H, then n equals 1.

Particularly preferred is where each hydrocarbyl group is, independently, a primary alkyl group, especially one containing from 1 to about 6 carbon atoms.

In another embodiment, the hydroxylamine has the general formula

wherein each R_c is, independently, H or a hydrocarbyl group, particularly, H or a lower alkyl group, provided that neither R_c is a strained ring group, each R is, independently, a lower alkylene group, preferably an ethylene or propylene group, most preferably, an ethylene group, and x ranges from 1 to about 29, preferably, from 1 to about 5.

Examples of hydroxylamines, which hydroxylamine have been found to be useful as supplemental combustion improvers in the fuel compositions of this invention, and methods for preparing them are described in numerous Unites States patents including, for example, US. 3,491,151; U.S. 4,017,512; US.5,731,462; U.S. 5,733,935 and U.S.6,031, 130. It should be noted that these patents also describe embodiments which are not contemplated as being part of the instant invention and it is not intended that such embodiments are to be considered as being part of the instant invention. These patents are hereby incorporated herein by reference for descriptions of the hydroxylamines that are described herein as useful in this invention.

In another preferred embodiment, the fuel composition further comprises a hydroxylamine salt. Hydroxylamines from which the hydroxylamine salts are derived are the same as the hydroxylamines described hereinabove. Typically, the salt is at least one member of the group consisting of nitrates, sulfates, sulfonates, carbonates and carboxylates. Nitrates and carbonates are preferred with nitrates being particularly preferred. The salts are generally obtained by contacting a hydroxylamine with an appropriate acid, optionally, in the presence of a diluent. Many of these salts are commercially available, for example, from chemical supply houses such as Aldrich Chemical Company, Milwaukee, WI, USA.

Other supplemental combustion improvers may be used together with the strained ring compounds of this invention including, for example, peroxides, for example t-butylperoxide and nitro compounds, usually lower alkyl nitro compounds, for example nitropropane. The Fuels

The fuels of this invention include all normally liquid hydrocarbon based fuels known in the art. By 'normally liquid' is meant a fuel which is liquid or liquefiable at normal operating temperatures. By 'hydrocarbon 'based' means the fuel contains hydrocarbon moieties. These fuels include gasoline meeting ASTM Specification D-4814, diesel fuel meeting ASTM Specification D-975, heating oil meeting ASTM Specification D-396, oxygenates, mixtures of predominantly hydrocarbon fuels and oxygenates, biomass fuel, emulsified mixtures of water and hydrocarbon based fuel and synthetic fuels.

Hydrocarbon based fuels are those fuels that contain hydrocarbon groups, and especially those that are substantially hydrocarbon, that is, those fuels derived from mineral oil sources such as gasoline and middle distillate oils, for example, diesel oil and heating oils, synthetic hydrocarbon fuels such as polyolefins, alkylated aromatic hydrocarbon group containing fuels, hydrocarbon fuels obtained by the Fischer-Tropsch process, and others.

Mixtures of hydrocarbon based fuels and oxygenates include mixtures of any of the aforementioned hydrocarbon based fuels with any of alkanols, especially lower alkanols, and ethers, for example, methyl-t-butyl ether, methyl-t-amyl ether, dimethoxymethane and diethoxymethane, and particularly, lower alkanols such as ethanol.

Biomass fuels are derived from organic materials, such as seeds. Processes for obtaining these oils from biomass are described in numerous U.S. Patents, many of which are listed in U.S. Patent 6,166,231 which is hereby incorporated herein by reference for relevant disclosures of such oils and methods for obtaining them. Examples of biomass fuels are biodiesel fuels, fuels containing ethanol and methanol, and vegetable oil, for example, sunflower oil and rapeseed oils. Emulsified fuels are typically emulsions prepared from hydrocarbon based fuels and water. Any type of emulsified fuel is useful. The emulsions may be of the water in oil (water in hydrocarbon based fuel) or oil in water (hydrocarbon based fuel in water) type. Invert emulsions, that is, water in oil emulsions, are preferred. The emulsified fuels may also comprise mixtures of fuels as discussed hereinabove. Oxygenates, as described hereinabove, may be included in the emulsified fuels.

As noted hereinabove, the fuel may be an emulsified mixture of water and hydrocarbon fuel, and optionally, mixtures of hydrocarbon fuels and any of the other types of fuels, such as oxygenates, etc. enumerated hereinabove. The incorporation of water is accomplished with an emulsifying agent. Many useful emulsifiers are known in the art. Several types are described in the aforementioned PCT Patent Publication WO 00/105740.

Emulsified fuels typically contain water in amounts ranging from about 0.1% to about 40% by weight based on the total weight of the emulsified fuel. In one embodiment, the emulsion may be a microemulsion, an emulsion that is generally clear in appearance. Such microemulsions generally contain water in amounts ranging from about 0.1 to about 5% by weight based on the total weight of the emulsified fuel.

In another embodiment, the emulsion is a macroemulsion. These are usually cloudy or milk-like in appearance. Such macroemulsions can be prepared by vigorously mixing of the components. Macroemulsion fuel compositions of this invention usually contain water in amounts ranging from about 2% or from about 5% to about 40% by weight based on the total weight of the emulsified fuel, often from about 2% to about 30%, or from about 10% up to about 30% and often from about 15% up to about 25% by weight.

A commercially available emulsified diesel fuel is marketed by the Lubrizol

Corporation, Wickliffe, Ohio, USA under the name PuriNOx (TM) fuel. In one embodiment of this application the fuel composition is substantially free of emulsified water such that the water content is less than 2, 1, or 0.5 wt.% based on the total weight of the composition.

The fuel compositions of the present invention may contain other additives which are well known to those skilled in the art. These can include supplemental combustion improvers such as those mentioned hereinabove, combustion modifiers, such as octane number enhancers for gasoline, foe example, anti-knock agents such as tetra-alkyl lead compounds and certain ethers, cetane number improvers for diesel fuels such as alkyl nitrates, lead scavengers such as halo-alkanes, dyes, antioxidants such as hindered phenols, lubricity agents, cold flow improvers, dispersants, surfactants, rust inhibitors such as alkylated succinic acids and anhydrides and derivatives thereof, bacteriostatic agents, auxiliary dispersants and detergents, gum inhibitors, fluidizers, metal deactivators, demulsifiers, anti-icing agents, corrosion inhibitors, and the like. The fuel compositions of this invention may be lead- containing or lead-free fuels. Preferred are lead-free fuels.

The following examples illustrate several compositions of this invention. All parts are parts by weight. These examples are intended to be for the purpose of illustration only, and are not intended to be limiting of the scope of the claims. Unless indicated otherwise, all amounts of components are given on a neat, diluent- free basis. Examples 1-3

Fuel compositions are prepared by blending into a test gasoline 5000 ppm of the indicated components:

Example 4

A fuel composition is prepared by blending into a test gasoline 1% by weight (10,000 ppm) of l-methoxy-2-methylpropyleneoxide.

Examples 5-7 Fuel compositions are prepared by blending into a test gasoline the listed amounts of the indicated component(s):

Examples 8-11

A mixture of 90% by weight gasoline and 10% by weight anhydrous ethanol is prepared. Fuel compositions are prepared by blending into the gasoline-ethanol mixture the listed amounts of the indicated components:

Examples 12-14

A mixture of 75% by weight gasoline and 25% by weight anhydrous ethanol is prepared. Fuel compositions are prepared by blending into the gasoline-ethanol mixture the listed amounts of the indicated components:

Examples 15-16

Example 17 A fuel composition is prepared by blending into a low sulfur #2 diesel fuel

5000 ppm of dicyclopropyl ketone. It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. For instance, metal ions (of, e.g., a detergent) can migrate to other acidic sites of other molecules. The products formed thereby, including the products formed upon employing the composition of the present invention in its intended use, may not susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the present invention; the present invention encompasses the composition prepared by admixing the components described above.

Each of the documents referred to above is incorporated herein by reference. Except in the examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word "about". Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. As used herein, the expression "consisting essentially of permits the inclusion of substances which do not materially affect the basic and novel characteristics of the composition under consideration.

While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications that fall within the scope of the appended claims.

Claims

What is claimed is

1. A fuel composition comprising a major amount of a normally liquid hydrocarbon based fuel and a minor amount of a compound having at least one strained ring group containing from 3 to 4 ring atoms per ring.

2. The fuel composition of claim 1 wherein the ring group is a hydrocarbyl group substantially free of heteroatoms.

3. The fuel composition of claim 1 wherein the ring contains both carbon atoms and heteroatoms, said heteroatoms being selected from the group consisting of O and N.

4. The fuel composition of claim 3 wherein the ring contains at least two carbon atoms.

5. The fuel composition of claim 4 wherein the ring contains no more than 2 heteroatoms.

6. The fuel composition of claim 5 wherein the ring contains only one heteroatom being oxygen.

7. The fuel composition of claim 2 wherein the hydrocarbyl group is a cyclopropyl group or a cyclobutyl group.

8. The fuel composition of claim 1, wherein said compound comprises bicyclopropyl or a lower alkyl (C1-C5) mono or di-substituted bycyclopropyl compound..

9. The composition of claim 6 wherein the ring is an epoxy group or an oxetane group.

10. The fuel composition of claim 1 wherein the compound comprises at least two strained ring groups.

11. The fuel composition of claim 10 wherein the compound has two strained ring groups.

12. The fuel composition of claim 11 wherein the two strained ring groups are fused bicyclo groups or spirocyclic groups.

13. The fuel composition of claim 10 wherein the strained ring groups are hydrocarbyl groups substantially free of heteroatoms.

14. The fuel composition of claim 13 wherein the compound comprises dicyclopropyl ketone or dicyclobutyl ketone.

15. The fuel composition of claim 7 wherein the compound comprises cyclopropyl methanol, cyclobutyl amine and cyclobutyl hydroxylamine.

16. The fuel composition of claim 9 wherein the compound is selected from the group consisting of 3,3-dimethyloxetane and l-methoxy-2-methylpropylene oxide.

17. The fuel composition of claim 8 wherein the compound comprises 3,3- dimethyloxetane.

18. The fuel composition of claim 1 further comprising a hydroxylamine wherein the hydroxylamine has the general formula

wherein each of R_a and R_b is, independently, a member selected from the group consisting of H, a primary hydrocarbyl group and a secondary hydrocarbyl group, and n ranges from 1 to about 30.

19. The fuel composition of claim 1 further comprising a hydroxylamine wherein the hydroxylamine has the general formula

wherein each R_c is, independently, H or a hydrocarbyl group, each R_d is, independently, a lower alkylene group and x ranges from 1 to about 29.

20. The fuel composition of claim 1 further comprising a hydroxylamine salt.

21. The fuel composition of claim 20 wherein the salt is at least one member of the group consisting of nitrates, sulfates, sulfonates, carbonates and carboxylates.

22. The fuel composition of claim 1 further comprising a nitro compound.

23. The fuel composition of claim 1 wherein the fuel comprises gasoline meeting ASTM Specification D-4814.

24. The fuel composition of claim 1 wherein the fuel comprises diesel fuel meeting ASTM Specification D-975.

25. The fuel composition of claim 1 wherein the fuel comprises heating oil meeting ASTM Specification D-396.

26. The fuel composition of claim 1 wherein the fuel comprises oxygenates.

27. The fuel composition of claim 26 wherein the oxygenates comprise at least one member of the group consisting of lower alkanols and ethers.

28. The fuel composition of claim 1 wherein the fuel comprises a mixture of a hydrocarbon fuel and a lower alkanol.

29. The fuel composition of claim 28 wherein the hydrocarbon fuel is gasoline.

30. The fuel composition of claim 28 wherein the hydrocarbon fuel is diesel fuel.

31. The fuel composition of claim 1 wherein the fuel comprises a biomass fuel.

32. The fuel composition of claim 31 wherein the biomass fuel comprises biodiesel fuel.

33. The fuel composition of claim 31 wherein the biomass fuel comprises vegetable oil.

34. The fuel composition of claim 1 wherein the fuel comprises an emulsified mixture of water and a hydrocarbon fuel.

35. The fuel composition of claim 34 wherein the emulsion comprises a water in fuel emulsion.

36. The fuel composition of claim 34 wherein the emulsion comprises a fuel in water emulsion.

37. The fuel composition of claim 34 wherein the emulsion is a microemulsion wherein water is present in amounts ranging from about 0.1% to about 5% by weight of the fuel composition.

38. The fuel composition of claim 34 wherein the emulsion is a macroemulsion wherein water is present in amounts ranging from about 2% to about 30% by weight of the fuel composition.

39. The fuel composition of claim 34 further comprising an oxygenate.

40. The fuel composition of claim 34 wherein the hydrocarbon fuel is gasoline.

41. The fuel composition of claim 34 wherein the hydrocarbon fuel is diesel fuel.

42. The fuel composition of claim 34 wherein the emulsified fuel is an invert emulsion.

43. The fuel composition of claim 1 wherein the fuel is a synthetic fuel.

44. The fuel composition of claim 43 wherein the synthetic fuel is obtained by the Fischer-Tropsch process

45. The composition of claim 43 wherein the synthetic fuel is a hydrocarbon fuel.

46. A method for improving the combustion characteristics of a normally liquid hydrocarbon based fuel comprising incorporating therein a combustion improving amount of a compound having at least one strained ring group containing from 3 to 4 ring atoms.

47. The fuel composition of claim 1 wherein the strained ring compound is present in amounts ranging from about 50 to about 50,000 parts by weight per million parts by weight of fuel.

48. The fuel composition of claim 1 further comprising at least one component selected from the group consisting of a) dispersants, b) combustion modifiers, c) lubricity agents, d) cold flow improvers, e) fluidizers, (f) surfactants and g) corrosion inhibitors.

49. The method of claim 46 wherein the improved combustion characteristics comprise at least one of reduced particulate emissions, reduced NO_x emissions, improved fuel efficiency and reduced hydrocarbon emissions.

50. A method for operating an internal combustion engine or a burner comprising providing to the combustion chamber of said engine or burner during operation thereof, the fuel composition of claim 1.