WO2005093016A1

WO2005093016A1 - Hydrocarbon fuels having improved combustion characteristics

Info

Publication number: WO2005093016A1
Application number: PCT/US2005/005507
Authority: WO
Inventors: Jianfeng Lou; Michael Jeffrey Lindstrom; Nicholas Michael Martyak
Original assignee: Arkema Inc.
Priority date: 2004-03-18
Filing date: 2005-02-22
Publication date: 2005-10-06
Also published as: TW200604334A

Abstract

Disclosed is the use of amine oxides as multifunctional additives for hydrocarbon fuels. Such additives are amine N-oxides that correspond to tertiary alkyl amines or tertiary alkyl alkanol amines. The amine oxide compound imparts to the fuel product improved combustion performance and reduced exhaust emissions.

Description

HYDROCARBON FUELS HAVING IMPROVED COMBUSTION CHARACTERISTICS

BACKGROUND OF THE INVENTION

Field of the Invention

[001] The present invention relates to improvements in hydrocarbon fuels, wherein the improvement is the addition of an effective amount of an amine oxide to the hydrocarbon fuel which improves the fuels combustion characteristics.

Prior Art

[002] It is well lαiown to include additives in hydrocarbon fuel to impart improved characteristics to the fuel. The following references are examples of known additives with their purposes.

[003] Bouffard, R. A.; US Patent Number 3,594,139, discloses the use of tertiary amine oxide as rust inhibitor for gasoline. Examples of rust inhibitors include bis (2-hydroxyethyl) cocoamine oxide, bis (2-hydroxyethyl) stearylamine oxide, and dimethylcocoamine oxide.

[004] Hashimoto, J.; Nomoto, S.; US Patent Number 5,298, 038, discloses an amine additive as cleaning agent for fuel systems and combustion chambers. Such an amine comprises a long chain alkyl (C9-C37) group with a branched alkyl (C3-C18) chain and an amine or an amine oxide containing at least one (C2-C4) polyoxyalkylene group. The additive is claimed to be effective in cleaning the injection nozzle of a diesel engine.

[005] Coughenour, G. E.; Kesling, H. S.; Liotta, Jr., F. J.; McFarland, J. M.; Nandi, M. K.; Chemtech, 27 (8), 38-41, 1997 describes the use of di-tert-butyl peroxide as a diesel fuel additive to increase the cetane number and reduce air pollutant emissions. [006] Schwab, S. D.; US Patent Number 5,669,938, discloses an emulsified fuel composition containing hydrocarbon fuel, water and emission-reducing additive. The compositions provide benefits of reduced exhaust emissions such as nitrogen oxides, carbon monoxide and particulate matter. The disclosed additive is an organic nitrate combustion improver such as 2-ethylhexyl nitrate.

[007] Bell, D. R.; US Patent Number 5,591,237, discloses a fuel additive composition containing a detergent, an organic nitrate combustion modifier, and a corrosion inhibitor. The combustion improver is a nitrate ester of aliphatic or cycloaliphatic alcohols. The fuel additive concentrate package is claimed to have enhanced shelf life stability when it is treated by acid such as nitric acid and hydrochloric acid.

[008] Daly, D. T.; Langer, D. A.; Baker, M. R; Wolak, T. J.; WO 02/068334, describes the use of many nitrogen-containing compounds as combustion modifier for emulsified fuel products. The disclosed combustion improvers include hydroxylarhines (or their salts) such as diethylhydroxylamine, nitro compounds such as nitrobenzene, strained ring containing compounds such as dioxolane and furan, nitrites such as toluene dinitrite, and nitramin.es such as benzyl nitramine. These combustion-improving additives are claimed to reduce the emission of air pollutants such as nitrogen oxides and particulate matter.

[009] Lif, A.; Olsson, S.; WO 02/48294, describes a microemulsion fuel composition with a nitrogen-containing surfactant as additive. The surfactant is based on an amine, an ether amine, an amine oxide or an amido compound, and it imparts improved storage stability to the emulsified fuel product.

[0010] As disclosed above, many additives have been developed aiming to improve the combustion performance, corrosion inhibition and storage stability of hydrogen carbon fuel compositions. Among such additives, nitrogen-containing compounds are commonly used. These nitrogen additives include fatty amines, amine oxides, hydroxylamines, nitro compounds, nitrates and nitrites, and they are often formulated into the final composition to produce emulsified fuel products.

[0011] The use of amine oxides as fuel additive has focused on their surface chemical properties, for example, their emulsifying, solubilizing and corrosion-inhibiting abilities. In the present invention, we disclose the application of amine oxides as fuel additives which serve, in part, as combustion improvers. The additive is an N-oxide or a mixed N-oxides corresponding to alkyl amine or alkyl alkanol amine, and it may act with conventional combustion improvers such as organic peroxide, nitrate, nitrite, hydroxylamine and dioxolane. The amine oxide additive provides numerous benefits for the hydrocarbon fuel product, in particular, enhanced fuel - performance through lower combustion temperatures and reduced pollutant emissions.

[0012] New federal regulations require improved combustion performance and reduced hazardous emissions for hydrocarbon fuels. The reduction of harmful emissions, in particular, has been a key driver in the marketplace as undesired chemicals such as nitrogen oxides, unburned hydrocarbons, carbon monoxide, and particulate matter contribute to air pollution. To meet governmental emission standards, fuel technology providers have developed emulsified hydrocarbon fuel products and nitrogen oxides trapping technologies. In addition, a variety of additives have been explored to enhance fuel performance and minimize harmful emissiorxs.

[0013] The present invention is directed to amine oxides additives which improve the combustion characteristics of fuels while also improving other properties as well. The disclosed amine oxides impart to fuel compositions enhanced combustion performance by lowering combustion temperatures. Lower combustion temperatures provide for reduced pollutant emissions, and improved cleaning abilities. SUMMARY OF INVENTION

[0014] The present invention is directed toward the use of amine oxides as multifunctional additives for hydrocarbon fuels. Such additives are amine N-oxides that correspond to tertiary alkyl amines or tertiary alkyl alkanol amines. The amine oxide compound is present from about 0.5-10 parts by weight per 100 parts of the formulated fuel composition, and it imparts to the fuel product improved combustion performance through reduced combustion temperatures and reduced exhaust emissions. Particularly, the use of amine oxide additive leads to decreased combustion temperatures which can result in lower emissions of air pollutants such as nitrogen oxides and particulate matter from combustion engines. In addition, the amine oxide additive can work in combination with other conventional combustion improvers such as 2-ethylhexyl nitrate, hydroxy ammonium nitrate, and di-tert-butyl peroxide.

DETAILED DESCRIPTION OF THE INVENTION

[0015] For fuel compositions with improved combustion performance and reduced harmful emissions, water is typically present in the product as a heat sink to lower peak combustion temperature, leading to decreased emission of nitrogen oxides and particulate matter. In addition, many additives are used in the formulation to enhance the fuel performance, improve storage stability, and provide corrosion inhibition. In particular, combustion improvers are used in order to reduce exhaust emissions such as nitrogen oxides, carbon monoxide, and particulate matter. Many combustion improvers are able to produce hydroxy radicals that interact with soot and other radicals to mitigate emission of air pollutants.

[0016] In the present invention, amine oxides are disclosed as multifunctional fuel additives for hydrocarbon fuels. Amine oxides are expected to generate hydroxy radicals which are believed to interact with soot, absorb heat to lower peak combustion temperature, function as surfactants to emulsify and solubilize, and supply oxygen internally to boost combustion performance. As such, the use of amine oxide additives can lead to decreased particulate formation, reduced NOx emission, improved chamber cleaning, and enhanced combustion performance. In addition, the presence of amine oxide additives could allow for the use of lower levels of other components such as surfactants and water. A lower level of water in the composition normally translates into improved fuel efficiency based on unit weight of the formulated fuel product. [0017] Amine N-oxide additives useful in this invention are oxidation products corresponding to a tertiary alkyl amine or a tertiary alkyl alkanol amine. A trialkyl amine N-oxide has the general formula:

N / \ R₂ R₃

where Ri, R2 and R₃ could be the same or different, and they could be alkyl, cycloalkyl, aryl, heteroaryl, hydroxyalkyl, and alkoxyalkyl groups. These alkyl groups could be cyclic or branched, and each group could have a carbon number between 1-26.

[0018] Tertiary alkyl alkanol amine oxides have one of the following three general formulas:

I. monoalkanol II. Dialkanol III. trialkanol amine oxide amine oxide amine oxide

The three formulas represent monoalkanol, dialkanol and trialkanol amine oxides, respectively. With monoalkanol amine oxide, ₄ and R₅ are alkyl or alkoxyalkyl groups with a carbon number between 1-12. They could be the same or different and could be cyclic or branched. R_a is an alkyl group with a carbon number between 1-18. With dialkanol amine oxide, R₆ is an alkyl or alkoxyalkyl group with a carbon number between 1-18. R_b and R_c are alkyl groups with a carbon number between 1-10, and they could be the same or different. With trialkanol amine oxide, R_a, R_b and R_c could all be the same or different. [0019] In the preferred embodiment, the amine oxide additive is incorporated into hydrocarbon fuel at concentrations of form about 0.5-10% by weight. The amine oxide is preferably added to the hydrocarbon fuel an aqueous solution of from about 62% to less than about 84% by weight amine oxide in water to provide the desired concentration of amine oxide in the hydrocarbon fuel. The resulting fuel composition is preferably an emulsified product, and it could contain additional additives such as surfactants, corrosion inhibitors, and anti-microbial agents.

[0020] It is preferred that the amine oxide additive is present at 0.5-1 wt.% of the fuel product. The preferred amine oxides are tri-(Cl-C4)-alkyl amine oxides, and (Cl-C4)-alkyl (C2-C3) alkanol amine oxides. Examples of such amine oxides include triethyl amine oxide, tripropyl amine oxide, diethyl hydroxyethyl amine oxide, dibutyl hydroxyethyl amine oxide, and butyl bishydroxyethyl amine oxide.

[0021] The amine oxide additive may be used in combustion modifiers to enhance the combustion performance while reducing pollutant emissions. Such combustion improvers include but are not limited to organic peroxides such as di-tert-butyl peroxide, nitrates such as 2- ethylhexyl nitrate, nitrites such as toluene dinitrite, hydroxylamines such as diethyl hydroxylamine, and nitro compounds such as dinitrotoluene.

[0022] In practice, it is preferable to mix the amine oxide of the present invention with other additives to prepare an additive concentrate package prior to introduction to the final fuel composition.

[0023] In the fuel formulation, one or more amine oxides can be used as additives. The amine oxides could be introduced to the formulation separately, or they could be premixed with other additives prior to their addition.

[0024] The disclosed fuel composition could be altered in that water may not be present in the formulation. Hydrocarbon fuels used in the present invention could be derived from natural oil sources such as minerals, vegetables and animal fats, and such common hydrocarbons include gasoline, diesel oil and heating oil. The hydrocarbon fuels could also be synthetic polyolefins and alkylated aromatics. In addition, the aforementioned hydrocarbon fuels could be mixed with oxygenated solvents such as alkanols and ethers. For example, substantial hydrocarbons are often blended with ethanol or methyl tertiary butyl ether for use as liquid fuel.

[0025] In the fuel composition, many types of other additives could be used depending on target product application. These additives include anti-microbial agents, corrosion inhibitors, antifreeze agents, emulsifiers and lubricants.

[0026] The following experiments involve preparation of emulsified hydrocarbon fuel compositions and measurement of combustion temperatures. A commercial emulsified diesel fuel supplied by Total (Paris, France) was used throughout the experiments.

EXAMPLE 1

[0027] An amine N-oxide combustion modifier was incorporated into diesel fuel at varying concentrations. After mixing an aqueous solution of 62% by weight triethylamine oxide (TEAO) with emulsified diesel fuel, pressure differential scanning calorimetry (DSC) was used to determine the temperature of the onset of combustion. The pressure DSC rans were made using a heating rate of 10° C per minute to 500° C in an open aluminum pan under an oxygen atmosphere at a pressure of 500 psi. The experimental results are summarized in Table 1. TABLE 1

SAMPLE ONSET OF COMBUSTION Diesel fuel 204° C Diesel fuel + 0.25% TEAO 204° C Diesel fuel + 0.50% TEAO 198° C Diesel fuel + 1.0% TEAO 197° C Diesel fuel + 5.0% TEAO 197° C

As seen in Table 1, the addition of the trialkyl amine N-oxide, TEAO reduced the onset of combustion by about 3%. EXAMPLE 2 [0028] Aqueous solutions of triethylamine oxide (TEAO) of varying concentrations were added to diesel fuel to provide a final concentration if TBAO in the diesel fuel of 1%, 5% and 10%) by weight. It was found that when higher concentrations of the aqueous TEAO were used to provide a higher final concentration of TEAO in the diesel fuel, a brown gel could form. Table 2 summarizes the results.

TABLE 2

[0029] Wliile the present invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be constmed to cover all such obvious forms and modifications which are within the tnxe spirit and scope of the present invention.

Claims

1. A method for improving the combustion of hydrocarbon fuels, wherein the improvement comprises adding an effective amount of an amine oxide to the hydrocarbon fuel.

2. The method of claim 1 wherein said amine oxide is selected from the group consisting of tertiary alkyl amines and tertiary alkyl alkanol amines.

3. The method of claim 1 wherein said amine oxide is selected from the group consisting of trialkyl amine N-oxides of the general formula:

N / \ R₂ R₃

wherein K_\, R2 and R are the same or different, and selected from the group consisting of cyclic or branched alkyl, cycloalkyl, aryl, heteroaryl, hydroxyalkyl, and alkoxyalkyl groups, having a carbon number between 1-26.

4. The method of claim 1 wherein said amine oxide is selected form the group consisting of monoalkanol amine oxides, dialkanol amine oxides and trialkanol amine oxides.

5. The method of claim 1 wherein said effective amount of said amine oxide comprises from about 0.5% to about 10%> by weight of said hydrocarbon fuel.

6. The method of claim 1 wherein said hydrocarbon fuel further comprises additives selected from the group consisting of surfactants, corrosion inhibitors, and anti-microbial agents.

7. The method of claim 1 wherein said hydrocarbon fuel is diesel fuel.

8. The method of claim 5 wherein said amine oxide is added as an aqueous solution of from about 64 %wt to less than 84 %wt amine oxide in water