FIELD OF THE INVENTION This invention relates to combustion improving additives for normally liquid fuels.

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.

Overall performance of a vehicle is known as'driveability'. Specifically, 'driveability'of a vehicle has been defined as the degree to which a vehicle starts readily, idles evenly, drives smoothly when cruising and accelerating, and generally responds to the throttle. Ambient temperatures during which a vehicle is operated have an effect on driveability. Driveability is also affected by fuel-air mixture ratio and by emission controls. Some lower grade fuels can adversely affect driveability.

A discussion of driveability appears in K. Owen and T. Coley,"Automotive Fuels Reference Book", Second Edition, Society of Automotive Engineers (Pub.), 1995, pp 173-181.

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

U. S. Patent 2,314,137 describes organic hydroxylamines as a class of compounds which, when added in minor proportions to Diesel fuel, are effective to decrease the ignition delay period and thereby improve the ignition quality of the fuel and the consequent operation of the engine in which it is used.

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 tolylaiazole 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 carbonyl 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 Cl 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.

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 hydroxylamine or a salt thereof. More often, each hydroxylamino group of the hydroxylamine or salt thereof contains no more than one tertiary alkyl substituent.

The hydroxylamine or salt thereof provides improved combustion properties to a

wide variety of normally liquid hydrocarbon based fuels, including fuels such as hydrocarbon fuels, biomass fuels and oxygenates. 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 hydroxylamine or a salt thereof.

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.

Hydroxylamines and Salts thereof The fuel compositions of this invention comprise at least one hydroxylamine or a salt thereof. More often, each hydroxylamino group of the hydroxylamine or salt thereof contains no more than one tertiary alkyl substituent.

In one embodiment, the hydroxylamine has the general formula

wherein each of Ra and Rb 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, 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 Ra 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 Re is, independently, H or a hydrocarbyl group, particularly, H or a lower alkyl group, each Rd 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 combustion improvers and methods for preparing them are described in numerous Unites States patents including, for example, U. S. 3,491,151; U. S. 4,017,512; U. S. 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 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.

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 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, for example, gasoline and middle distillate oils, 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 vegetable oil, for example, sunflower oil and rapeseed oils.

The fuel compositions of this invention comprise a minor amount of hydroxylamine or salt thereof. More typically, the fuel compositions comprise from about 50 to about 50,000 parts by weight, even more often from about 1,000 to about 10,000 or to about 5,000 parts by weight, hydroxylamine or salt thereof per million parts by weight of fuel.

The fuel compositions of the present invention may contain other additives which are well known to those skilled in the art. These can include combustion modifiers, such as octane number enhancers for gasoline, for 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 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.

Example 1 A fuel composition is prepared by mixing together, at high speed, 85 parts of a low sulfur No. 2 fuel oil, 15 parts anhydrous ethanol and 0.5 parts N, N- diethylhydroxylamine.

Example 2 A fuel composition is prepared by mixing together 100 parts of a low sulfur No. 2 fuel oil and 0.5 parts N, N-diethylhydroxylamine.

Example 3 A fuel composition contains 95 parts unleaded gasoline and 5 parts methanol emulsified with 1.0 part of a 1: 1 by weight mixture of a polyether amine prepared by reductive cyanoethylation of C12-15 substituted polyoxypropylene monool and a N, N- diethylhydroxylamine hexadecyl substituted succinic ester-salt prepared by reacting one mole each of hexadecyl substituted succinic anhydride with dimethylethanolamine to which emulsion is added 0.5 part N, N- diethylhydroxylamine.

Example 4 A fuel composition contains 96.33 parts diesel fuel, 1.0 parts C12-15 alkyl poly (oxypropyl) 24 propyl amine, 1 part hexadecenyl succinic dimethylaminoethyl ester-salt and 1.67 parts 13M aqueous hydroxylammonium nitrate.

Example 5 A fuel composition contains 99.50 parts gasoline and 0.5 part N, N- diethylhydroxylamine.

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.