WO2009108851A1

WO2009108851A1 - Biodiesel stabilizing compositions

Info

Publication number: WO2009108851A1
Application number: PCT/US2009/035452
Authority: WO
Inventors: Ibrahim Abou-Nemeh
Original assignee: Novus International Inc.
Priority date: 2008-02-29
Filing date: 2009-02-27
Publication date: 2009-09-03

Abstract

The present invention provides antioxidant compositions that increase the oxidative stability of biodiesel, stabilized fuel compositions, and methods of using the antioxidant compositions to increase the oxidative stability of fuel compositions.

Description

BIODIESEL STABILIZING COMPOSITIONS

FIELD OF THE INVENTION

[0001] The present invention generally relates to antioxidant compositions for increasing the oxidative stability of biodiesel. In particular, the invention provides antioxidant compositions, stabilized fuel compositions, and methods of using the antioxidant compositions to stabilize fuel compositions.

BACKGROUND OF THE INVENTION

[0002] The use and production of biodiesel as a possible alternative to vehicle fuel, heating fuel, and engine fuel has increased in recent years due to concerns with limited resources of fossil based fuels. Biodiesel is typically produced from the transestehfication of, for example, vegetable oils, animal fats, and used cooking oils.

[0003] Because biodiesel has a relatively high content of unsaturated fatty acid esters, it easily oxidizes in the presence of oxygen, UV light, heat, and trace metals. The products formed from this oxidation give rise to sediment and gum formation within the fuel and lead to corrosion and plugging in injection pumps and/or fuel lines in engines, heaters, and/or machines that utilize biodiesel as a fuel source.

[0004] As such, there is a need for a biodiesel fuel composition having improved oxidation stability that reduces or eliminates sedimentation and gum formation of the fuel, extends its shelf life by increasing the induction period, lowers the level of peroxides precursors of fuel auto-oxidation, and as such reduces or eliminates corrosion and plugging in injection pumps and/or fuel lines in engines.

SUMMARY OF THE INVENTION

[0005] Among the various aspects of the present invention is the provision of antioxidant compositions for stabilizing biodiesel compositions.

[0006] A first aspect of the invention encompasses a composition comprising at least one ethylene amine and at least one phenolic antioxidant.

[0007] Another aspect provides a composition consisting essentially of at least one ethylene amine, at least one phenolic antioxidant, and an aromatic solvent. [0008] A further aspect of the invention provides a composition comprising at least one phenolic antioxidant and a hydroxy dicarboxylic acid.

[0009] Still another aspect of the present invention encompasses a composition consisting essentially of at least one phenolic antioxidant and 2,3- dihydroxybutanedioic acid.

[0010] An additional aspect of the invention provides a composition comprising 2-tert-butylhydroquinone, 2,3-dihydroxybutanedioic acid, and an amine.

[0011 ] Yet another aspect of the present invention encompasses a composition consisting essentially of a phenolic antioxidant, 2,3-dihydroxybutanedioic acid, and an amine.

[0012] A further aspect of the invention provides method for increasing the oxidative stability of a fuel composition. The method comprises contacting the fuel composition with any of the antioxidant compositions of the invention.

[0013] Other aspects and features of the invention are described in more detail below.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention provides antioxidant compositions that may be used to improve the oxidative stability of biodiesel, which comprises fatty acid methyl esters (FAME). In particular, it has been discovered that certain formulations of phenolic antioxidants and chelating agents (i.e., amine and/or acidic chelating agents) are effective at stabilizing biodiesel. As illustrated in the examples, a composition comprising at least one phenolic antioxidant and at least one ethylene amine improve the oxidative stability of biodiesel more than either type of component alone. Furthermore, a composition comprising 2-tert-butylhydroquinone and tartaric acid stabilizes biodiesel more effectively than the combination of a phenolic antioxidant and citric acid. The antioxidant compositions of the invention, as such, may be beneficially utilized to improve the oxidative stability of biodiesel. (I) Antioxidant Compositions

[0015] As used in the context of the present invention, the term

"antioxidant composition" is used broadly to encompass compositions that comprise at least one phenolic antioxidant. The antioxidant composition will also typically include one or more compounds that may not be antioxidants. Minimally, antioxidant compositions of the invention generally comprise at least one phenolic antioxidant and at least one chelating agent. Examples of suitable chelating agents include amine containing chelating agents and acidic chelating agents. Thus, in some embodiments, the antioxidant compositions of the invention may comprise at least one phenolic antioxidant and at least one ethylene amine. In other embodiments, the antioxidant compositions may comprise at least one phenolic antioxidant, a dicarboxylic acid, and, optionally, at least one amine compound. In each of the foregoing embodiments, the antioxidant composition typically further comprises a solvent or a solvent mixture. Optionally, the antioxidant compositions of the invention may further comprise non- phenolic antioxidants.

(a) phenolic antioxidant

[0016] The antioxidant composition includes at least one phenolic antioxidant. In certain embodiments, the antioxidant composition may comprise two phenolic antioxidants. In an additional embodiment, the antioxidant composition may comprise three phenolic antioxidants. In another embodiment, the antioxidant composition may comprise four phenolic antioxidants. In still an additional embodiment, the antioxidant composition may comprise more than four phenolic antixoxidants.

[0017] Suitable examples of phenol compounds having antioxidant activity include mono, di, and trialkylated phenols such as 2-tert-butylphenol, 2,6-di-tert- butylphenol, 2,4-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol, and 2,6-di-tert-butyl-4- methylphenol (also known as butylated hydroxytoluene or BHT). Examples of bisphenol compounds having antioxidant activity include 2,2'-methylene-bis-(4-methyl-6-tert- butylphenol) (BKF), 2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol), 2,2'- methylenebis(6-tert-butyl-4-methyl-phenol), 2,2'-methylenebis(6-tert-butyl-4-ethyl phenol), and 4,4'-methylenebis(2,6-di-tert-butyl phenol). Some examples of diphenol compounds having antioxidant activity include hydroquinone (HQ), mono and dialkylated hydroquinones having one or two C1 -C8 alkyl groups (e.g. 2-tert- butylhydroquinone (TBHQ), 2,5-di-tert-butylhydroquinone (DTBHQ), methylhydroquinone (also known as 2-methylhydroquinone, toluhydroquinone or THQ), 2,5-di-tert-octylhydroquinone (DOH), alpha naphthol, catechol (also known as pyrocatechol) and mono and dialkylated catechols having one or two C1-C8 alkyl groups (e.g. tert-butylcatechol). Suitable examples of diphenol monoether compounds having antioxidant activity include 4-methoxyphenol (hydroquinone monomethyl ether, or HQMME)) and 2-methoxyphenol (guaiacol, or catechol monomethyl ether), butylated hydroxyanisole (BHA). Some examples of triphenol compounds having antioxidant activity include pyrogallol (1 ,2,3-trihydroxybenzene) and C1 -C18 esters of gallic acid such as n-propyl gallate, dodecyl gallate, or octyl gallate. In some embodiments, at least one triphenol compound is a C1 -C8 ester of gallic acid. In some embodiments, at least one triphenol compounds is pyrogallol. In other embodiment, the antioxidant may be a substituted 1 ,2-dihydroquinoline compound. Substituted 1 ,2-dihydroquinoline compounds suitable for use in the invention generally correspond to Formula (I):

(I) wherein:

R¹, R², R³ and R⁴ are independently selected from the group consisting of hydrogen and an alkyl group having from 1 to about 6 carbons; and

R⁵ is an alkoxy group having from 1 to about 12 carbons. [0018] In another embodiment, the substituted 1 ,2-dihydroquinoline will have Formula (I) wherein:

R¹, R², R³ and R⁴ are independently selected from the group consisting of hydrogen and an alkyl group having from 1 to about 4 carbons; and R⁵ is an alkoxy group having from 1 to about 4 carbons. [0019] In one preferred embodiment, the substituted 1 ,2-dihydroquinoline will be 6-ethoxy-1 ,2-dihydro-2,2,4-trimethylquinoline having the formula:

[0020] The compound, 6-ethoxy-1 ,2-dihydro-2,2,4-trimethylquinoline, commonly known as ethoxyquin, is sold under the trademark SANTOQUIN^®or AGRADO^®. The present invention also encompasses salts of ethoxyquin and other compounds having Formula (I). Ethoxyquin and other compounds having Formula (I) may be purchased commercially from Novus International, Inc. or made in accordance with methods generally known in the art, for example, as detailed in U.S. Patent No. 4,772,710, which is hereby incorporated by reference in its entirety.

[0021] In preferred embodiments, the phenolic antioxidant is selected from the group consisting of butylated hydroxyanisole (BHA); butylated hydroxytoluene (BHT); gallates such as octyl gallate, dodecyl gallate, and 3,4,5-trihydroxybenzoic acid n-propyl ester (propyl gallate); 1 ,2,3-thhydroxybenzene (pyrogallol); gallic acid; 2-tert- butylhydroquinone (TBHQ); mixtures of TBHQ (e.g., TENOX 20^® and TENOX 21^® by the company Eastman Chemical Company); 2-tert-butyl-phenol; 4,6-di-tert-butylphenol; 2,6-di-tert-butylphenol; 2,4,6-tri-tert-butyl phenol; 4-sec-butyl-2,6-di-tert-butylphenol 2,6- diisopropyl phenol; alpha naphthol, and ethoxyquin. In one exemplary embodiment, the phenolic antioxidant may be 2-tert-butyl-phenol. In another exemplary embodiment, the phenolic antioxidant may be 2-tert-butyl-phenol. In an alternate exemplary embodiment, the phenolic antioxidant may be a mixture of 2-tert-butyl-phenol and propyl gallate. In still another exemplary embodiment, the phenolic antioxidant may be 2-tert- butylhydroquinone (TBHQ). (b) other antioxidants

[0022] Optionally, in addition to at least one phenolic antioxidant detailed in l(a) above, the antioxidant composition may include additional antioxidants. For example, the antioxidant compositions may include natural antioxidants, synthetic antioxidants or semi-synthetic antioxidants.

[0023] Suitable antioxidants include fatty acid esters including, but not limited to, methyl esters such as methyl linoleate, methyl oleate, methyl stearate, and other esters such as ascorbic palmitate; disulfiram; tocopherols, such as gamma- tocopherol, delta-tocopherol alpha-tocopherol acetate, and alpha-tocopherol marketed under the name COPHEROL 1300^® by the company Henkel, and tocopherol derivatives and precursors, such as Coviox T-50 by the company Cognis; propionate esters and thiopropionate esters such as isopropyl 2-hydroxy-4-methylthio butanoate, lauryl thiodipropionate, or dilauryl thiodipropionate; beta-lactoglobulin; ascorbic acid; amino acids such as phenylalanine, cysteine, tryptophan, methionine, glutamic acid, glutamine, arginine, leucine, tyrosine, lysine, serine, histidine, threonine, asparagine, glycine, aspartic acid, isoleucine, valine, and alanine; 2,2,6,6-tetramethylpiperidinooxy, also referred to as tanan; 2,2,6,6-tetramethyl-4-hydroxypiperidine-1 -oxyl, also referred to as tanol; sage extract; eugenol; rosemary; flavonoids and derivatives (including catechins); imidazolidinyl urea, quaternary ammoniums, diazolidinyl urea; erythorbic acid; sodium erythorbate, lactic acid, calcium ascorbate, sodium ascorbate, potassium ascorbate, ascorbyl stearate, erythorbin acid; sodium erythorbin; butylhydroxinon; sodium or potassium or calcium or magnesium lactate; citric acid; sodium, monosodium, disodium or trisodium citrates; potassium, monopotassium or thpotassium citrate; stearyl citrate; palmityl citrate; tartaric acid; sodium, monosodium or disodium tartrates; potassium, monopotassium tartrate or dipotassium tartrate; sodium potassium tartrate; phosphoric acid; sodium, monosodium, disodium or trisodium phosphates; potassium, monopotassium, dipotassium and tripotassium phosphates; stannous chloride; chlorophyl; lecithin; nordihydroguaiaretic acid (NDGA); ascorbyl stearate; 1 -cysteine hydrochloride; gum guaiacum; lecithin citrate; monoglycehde citrate; monoisopropyl citrate; ethylenediaminetetraacetic acid; polyphosphates; thhydroxy butyrophenone; anoxomer; and combinations thereof. In yet another embodiment, the antioxidant may be a water-soluble antioxidant selected from the group comprising of ascorbic acid, sodium metabisulfite, sodium bisulfite, sodium thiosulfite, sodium formaldehyde sulfoxylate, isoascorbic acid, thioglyerol, thiosorbitol, thiourea, thioglycolic acid, cysteine hydrochloride, 1 ,4-diazobicyclo-(2,2,2)-octane, malic acid, fumaric acid, and licopene.

(c) amine chelating agent

[0024] In some embodiments, the antioxidant composition of the invention comprises an amine compound. The amine may be an ethylene amine. Non-limiting examples of suitable ethylene amines include, ethylene diamine (EDA), N- hydroxyethylethylenediamine, aminoethyl ethanolamine (AEEA), diethylenetriamine (DETA), triethylenetetraamine (TETA), tetraethylenepentaamine (TEPA), pentaethylenehexamine (PEHA), piperazine, aminoethyl piperazine, N-methyl piperazine, hydroxyethyl piperazine, polyamine B, and heavy polyamine X (HPX). In preferred embodiments, the ethylene amine may be tetraethylenepentaamine (TEPA) or pentaethylenehexamine (PEHA).

[0025] In alternate embodiments, the amine may be a non-ethylene amine.

Non-limiting examples of suitable non-ethylene amines include amino alcohols such as mono-, di-, and tri-ethanolamines; polyamines such as putrescine, spermidine, and the like; aminocarboxylic acid chelators such as ethylenediaminetetraacetic acid (EDTA); aliphatic amines; and aromatic amines. In an exemplary embodiment, the amine is selected from the group consisting of 2-(2-aminoethylamino)ethanol, N₁N'- bis(salicylidene)-1 ,3-propanediamine, N,N'-diphenyl-1 ,4-phenylenediamine, ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylene diamine-N,N',N'-triacetic acid, N,N,N',N'-tetraacetic acid, ethylenediamine-N,N'diacetic acid, trans-1 ,2- diaminocyclohexane,diethylenethaminepentaacetic acid, and N,N'-di-sec-butyl-1 ,4- phenylenediamine. In an exemplary embodiment, the amine may be N,N'-di-sec-butyl- 1 ,4-phenylenediamine (DPA).

(d) acidic chelating agent

[0026] In other embodiments, the antioxidant composition may comprise an acidic chelating agent. Non-limiting examples of suitable acidic chelating agents include monocarboxylic acids such as acetic acid, propionic acid, butanoic acid, and the like; dicarboxylic acids such as N-acetylglutamic acid, 1 ,3-acetonedicarboxylic acid, adipic acid, aldaric acid, alpha-keto-glutahc acid, L-aspartic acid, azelaic acid, camphoric acid, citraconic acid, D(-)-citramalic acid, creatine-alpha-ketoglutarate, cyclopropane-1 ,1 -dicarboxylic acid, diglycolic acid, dihydroxyfumaric acid, dimercaptosuccinic acid, dimethylmalonic acid, dithiodiglycolic acid, 3,4- ethylenedioxypyrrole-2,5-dicarboxylic acid, ethylmalonic acid, fumaric acid, glutaconic acid, L-glutamic acid, glutaric acid, isophthalic acid, itaconic acid, maleic acid, malic acid, malonic acid, meglutol, mesaconic acid, mesoxalic acid, meso-2,3- dimercaptosuccininc acid.S-methylglutoconic acid, methyliminodiacetic acid, methylmalonic acid, methylsuccinic acid, muconic acid, oxalic acid, oxaloacetic acid, pamoic acid, R-phenylsuccinic acid, phthalic acid, pimelic acid, sebacic acid, suberic acid, succinic acid, L(+)-tartahc acid (also known as 2,3-dihydroxybutanedioic acid), D(-)-tartahc acid, DL-tartahc acid, tartronic acid, (-)-trans-pyrrolidine-2,4-dicarboxylic acid, terephthalic acid, 2,2-thiodiacetic acid, 1 ,2,3-triazole-4,5-dicarboxylic acid, (+/-)- trans-cyclohexane-1 , 2, -dicarboxylic acid, trans-beta-hydromuconic acid, and traumatic acid; tricarboxylic acids such as citric acid, isocitric acid, aconitic acid, propane-1 ,2,3,- tricarboxylic acid, and the like; amino acid chelators such as aspartic acid, glutamic acid, methionine, and the like. The acidic chelating agent may be a free acid. Alternatively, the acidic chelating agent may be a salt or an ester of the free acid, such as, for example, sodium tartrate, stearyl tartrate, triethyl citrate, monostearyl citrate, and the like.

[0027] In one embodiment, the acidic chelating agent may be a tricarboxylic acid, such as citric acid. In another embodiment, the acidic chelating agent may be a hydroxy dicarboxylic acid. Examples of hydroxy dicarboxylic acids include tartaric acid (i.e., 2,3-dihydroxybutanedioic acid) and malic acid (i.e., hydroxybutanedioic acid). In an exemplary embodiment, the hydroxy dicarboxylic acid may be tartaric acid (2,3-dihydroxybutanedioic acid). (e) solvents

[0028] The antioxidant composition of the present invention is typically dissolved in a solvent or a solvent system. In an exemplary embodiment, the selection of components (i.e., solvents, antioxidants, chelators) provides a homogeneous composition that is readily miscible in a fuel composition. In some embodiments, the solvent system may include a surfactant. In accordance, the solvents utilized in the invention may be a single compound or a combination of solvent compounds, such as in a solvent matrix. In some embodiments, the solvents are selected from monofunctional alcohols, glycols, polyols, esters, ethers, glycol ether acetates, ketones, glycol ethers, amides, nitro compounds and combinations of two or more of the foregoing. In other embodiments, the solvent may comprise an aromatic hydrocarbon solvent. Examples of each type of solvent are presented below.

[0029] In one embodiment, the solvent may comprise a monofunctional alcohol. Examples of monofunctional alcohols include C1 -C25 monofunctional alcohols, but also include monofunctional alcohols selected from smaller ranges such as C2-C25 alcohols, C2-C10 alcohols, C3-C10 alcohols, C3-C18 alcohols, C8-C18 alcohols, and so forth. Some examples of C3-C18 monofunctional alcohols include n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, amyl alcohol, 2-ethyl hexanol, decyl alcohol, and 1 - octadecanol. In an exemplary embodiment, the monofunctional alcohol is octanol or decanol.

[0030] In yet another embodiment, the solvent may comprise a compound that is a polyol. Suitable examples of polyol solvents include glycols such as ethylene glycol, polyethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol. In one exemplary embodiment, the polyol used is propylene glycol.

[0031] In an additional embodiment, the solvent may comprise a glycol ether compound. In the context of the present invention, "glycol ether" means a molecule having the structure of a glycol except that the molecule possesses an ether linkage to an alkyl group instead of one of the hydroxyl groups. Thus a monoalkyl ether of ethylene glycol, for example, has the structure of ethylene glycol with an ether linkage connected to an alkyl group instead of one of the two hydroxyl groups normally found on ethylene glycol. By way of further example, "ethylene glycol mono butyl ether" refers to a molecule having the structure of ethylene glycol with an ether linkage connected to a butyl group. In some embodiments, the glycol ether solvent includes 1-3 ether linkages and exactly one hydroxy (-OH) group. Suitable examples include C1 -C12 monoalkyl ethers of ethylene glycol, C1 -C12 monoalkyl ethers of diethylene glycol, C1 -C12 monoalkyl ethers of triethylene glycol, C1 -C12 monoalkyl ethers of propylene glycol, C1 -C12 monoalkyl ethers of dipropylene glycol, and C1 -C12 monoalkyl ethers of tripropylene glycol. Examples include ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2- ethylhexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, and combinations of two or more thereof.

[0032] In a further embodiment, the solvent may comprise a compound that is an ester. Examples of ester solvents include C3-C24 esters including, but not limited to methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate, amyl acetate, methyl amyl acetate, n-propyl propionate, n-butyl propionate, isobutyl isobutyrate, 2-ethylhexyl acetate, ethylene glycol diacetate, dimethyl adipate, dimethyl succinate, dimethyl glutarate, C12-C24 fatty acid methyl esters, propylene glycol diacetate (diacetoxypropane), and combinations of two or more thereof.

[0033] In a further embodiment, the solvent may comprise a compound that is a glycol ether ester compound. In some embodiments, the glycol ether ester compound is a C1 -C12 glycol ether ester compound, in which C1 -C12 refers to the number of carbons in the alkyl group attached to the ether linkage. Suitable examples include acetate esters of C1 -C12 monoalkyl ethers of ethylene glycol, the acetate esters of C1 -C12 monoalkyl ethers of diethylene glycol, the acetate esters of C1 -C12 monoalkyl ethers of triethylene glycol, the acetate esters of C1 -C12 monoalkyl ethers of propylene glycol, the acetate esters of C1 -C12 monoalkyl ethers of dipropylene glycol, and the acetate esters of C1 -C12 monoalkyl ethers of tripropylene glycol. In other embodiments, the glycol ether ester compound is selected from ethyl-3- ethoxypropionate, ethylene glycol monobutyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, and combinations of two or more thereof.

[0034] In another embodiment, the solvent may comprise a compound that is an ether compound. Some examples of solvents selected from the class of ethers include diisopropyl ether, tetrahydofuran (THF), dipropylene glycol dimethyl ether, and combinations of two or more thereof.

[0035] In an additional embodiment, the solvent may comprise a compound that is a ketone. Suitable examples of solvents selected from the class of ketones include straight or branched C3-C14 ketones. In some embodiments, ketones are selected from acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, cyclohexanone, methyl amyl ketone, and combinations of two or more thereof.

[0036] In a further embodiment, the solvent may comprise a compound that is an amide compound. In some embodiments, the amide is a C2-C10 amide. Some examples of solvents selected from the class of amides include N₁N- dimethylformamide (DMF), N-methylpyrrolidone and dimethylacetamide and combinations of two or more thereof.

[0037] In yet another embodiment, the solvent may comprise an aromatic hydrocarbon solvent. Non-limiting examples of suitable aromatic hydrocarbon solvents include aromatic naphtha solvents such as Aromatic 100, Aromatic 150, or Aromatic 200, which are available from ExxonMobil; toluene, xylene, and mixtures of xylene.

[0038] In some embodiments, the solvent may further comprise a surfactant or detergent. Suitable surfactants or detergents include, without limitation, polyisobutylene succinimides, polyisobutylene succinic anhydrides and derivatives thereof, polyether compounds (such as SURFONAMINE^® MW-781 amine, SURFONAMINE^® B100, and the like, which are available from Huntsman Corporation, The Woodlands, TX), polyether-polyol compounds (such as ACTACLEAR^® 2400, available from Bayer Material Science, Leverkusen, Germany), and epoxylated ester compounds.

(f) exemplary antioxidant compositions

[0039] The antioxidant compositions may include a variety of combinations of the components detailed in l(a) to l(e) without departing from the scope of the invention. Minimally, the antioxidant composition will include at least one phenolic antioxidant and at least chelating agent. In some embodiments, the chelating agent may be an ethylene amine. In other embodiments, the chelating agent may be a dicarboxylic acid. In further embodiments, the chelating agent may be a combination of a dicarboxylic acid and an amine. In further embodiments, the antioxidant composition may comprise two, or three or more phenolic antioxidants. Suitable non-limiting examples of antioxidant compositions are detailed in Table A.

Table A.

Table A.

Table A.

Table A.

Table A.

Table A.

[0040] As will be appreciated by a skilled artisan, the antioxidant composition may be in the form of a dry powder or suspended in a solvent. The antioxidant composition may include a variety of concentrations of phenolic antioxidants or combinations of phenolic antioxidants and non-phenolic antioxidants. In some embodiments, the concentration of antioxidant(s) may be at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or greater than 95% by weight of the composition. The concentration of antioxidant(s) may range from about 10% to about 20% by weight of the antioxidant composition, from about 20% to about 30% by weight of the antioxidant composition, from about 30% to about 40% by weight of the antioxidant composition, from about 40% to about 50% by weight of the antioxidant composition, from about 50% to about 60% by weight of the antioxidant composition, from about 60% to about 70% by weight of the antioxidant composition, from about 70% to about 80% by weight of the antioxidant composition, from about 80% to about 90% by weight of the antioxidant composition, or greater than about 90% by weight of the antioxidant composition. [0041] The concentration of the amine (i.e., ethylene amine and/or other amine) may range from about 5% to about 80% by weight. In some embodiments, the concentration of the amine may be about least 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, or about 80% by weight of the composition. The concentration of the amine may range from about 5% to about 20% by weight of the antioxidant composition, from about 20% to about 40% by weight of the antioxidant composition, from about 40% to about 60% by weight of the antioxidant composition, or from about 60% to about 80% by weight of the antioxidant composition. In one preferred embodiment, the antioxidant composition comprises an ethylene amine, and the concentration of the ethylene amine may range from about 50% to about 80% by weight, or more preferably from about 65% to about 80% by weight of the antioxidant composition.

[0042] The amount of dicarboxylic acid or the combination of dicarboxylic acid and another chelating agent (i.e., amine or acidic chelator) can and will vary. The amount may range from about 0.01 % to about 90% by weight of the antioxidant composition. In other embodiments, the amount may range from about 0.1 % to 5% by weight of the antioxidant composition, from about 5% to 10% by weight of the antioxidant composition, from about 10% to 15% by weight of the antioxidant composition, from about 15% to 20% by weight of the antioxidant composition, from about 20% to 25% by weight of the antioxidant composition, from about 25% to 30% by weight of the antioxidant composition, from about 30% to 35% by weight of the antioxidant composition, from about 35% to 40% by weight of the antioxidant composition, from about 40% to 45% by weight of the antioxidant composition, from about 45% to 50% by weight of the antioxidant composition, or greater than about 50% by weight of the antioxidant composition.

[0043] The solvent, if present, may comprise about 5%, about 10%, about

15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, or greater than about 90% by weight of the suspended antioxidant composition. [0044] In one exemplary embodiment, the antioxidant composition comprises from about 50% to about 80% by weight of tetraethylenepentamine or pentaethylenehexamine, from about 0% to about 10% by weight propyl gallate, from about 5% to about 20% by weight of 2-tert-butylphenol, and from about 5% to about 30% by weight of the aromatic naphtha solvent. In particular, one exemplary antioxidant composition comprises about 75% by weight of tetraethylenepentamine, about 5% by weight of propyl gallate, about 10% by weight of 2-tert-butylphenol, and about 10% by weight of aromatic naphtha solvent. Another exemplary antioxidant composition comprises about 75% by weight of pentaethylenehexaamine, about 5% by weight of propyl gallate, about 10% by weight of 2-tert-butylphenol, and about 10% by weight of aromatic naphtha solvent. Additional exemplary antioxidant compositions comprise about 60% by weight of tetraethylenepentamine or pentaethylenehexaamine, about 4% by weight of propyl gallate, about 8% by weight of 2-tert-butylphenol, and about 28% by weight of aromatic naphtha solvent.

[0045] In another exemplary embodiment, the antioxidant composition comprises from about 5% to about 40% by weight of 2-tert-butylhydroquinone, from about 0.5% to about 5% by weight of 2,3-dihydroxybutanedioic acid (i.e., tartaric acid), from about 1 % to about 10% by weight of octanol; and from about 45% to about 93.5% by weight of propylene glycol. In yet a further exemplary embodiment, the antioxidant composition comprises from about 5% to about 40% by weight of 2-tert- butylhydroquinone; from about 0.5% to about 5% by weight of tartaric acid; from about 5% to about 20% by weight of a phenolic antioxidant other than 2-tert- butylhydroquinone; from about 5% to about 40% by weight of an amine; from about 1 % to about 10% by weight of octanol; and from about 1 % to about 83.5% by weight of propylene glycol. Other exemplary antioxidant compositions are detailed in the examples.

(II) Uses of the Antioxidant Compositions

[0046] Generally speaking, the antioxidant compositions of the invention may be utilized to increase the oxidative stability of fatty acids or fatty acid esters. In exemplary embodiment, the antioxidant compositions are included in a fuel composition that includes a biodiesel. The biodiesel may be distilled or undistilled. Biodiesel suitable for use in the invention is typically an ester, such as a mono-alkyl ester, of long chain fatty acids derived from a lipid source. The lipid source may be naturally occurring, such as a lipid derived from a plant or animal, or it may be synthetically produced. In one embodiment, the biodiesel may be produced from vegetable oil, spent cooking oil, or animal fat. In one embodiment, the biodiesel may be produced from a vegetable oil. In another embodiment, the biodiesel may be produced from a vegetable oil selected from the group consisting of soybean oil, corn oil, rapeseed oil, coconut oil, peanut oil, palm oil, cottonseed oil, sunflower oil, mustard seed oil, camelina oil, jojoba oil, safflower oil, and hemp oil. Other vegetable oils may also be used without departing from the scope of the invention. In an exemplary embodiment, the biodiesel may be produced from soybean oil. In another exemplary embodiment, the biodiesel may be produced from rapeseed oil. In another embodiment, the biodiesel may be produced from plant oil, such as jatropha oil and algae oil. In a further embodiment, the biodiesel may be produced from spent cooking oil, such as used frying oil. In yet another embodiment, the biodiesel may be produced from animal fat selected from the group consisting of tallow, poultry fat, and lard. In still another embodiment, the biodiesel may be produced from yellow grease. In yet another embodiment, the biodiesel may be produced from a fish oil, such as menhaden oil, anchovy oil, and mackerel oil, among others. In a further embodiment, the biodiesel may be produced from marine oil, such as whale oil or shark oil. As will be appreciated by the skilled artisan, the biodiesel may also be produced from a combination of lipids derived from different sources. For example, the biodiesel may be produced from a mixture of soybean oil and animal fat.

[0047] A variety of methods generally known in the art may be used to make the biodiesel of the present invention from any lipid sources known in the art or identified herein. In general, biodiesel is produced through the transesterifcation of vegetable oils, spent cooking oils, or animal fats. Such methods may include base catalyzed transestehfication of the glycerides in the oil or fat with an alcohol, and acid catalyzed esterification of the free fatty acids in the oil or fat with an alcohol, wherein fatty acid alkyl esters are formed. In a base catalyzed transestehfication process, an oil or fat is reacted with an alcohol, such as methanol or ethanol, in the presence of a catalyst, such as sodium hydroxide, potassium hydroxide, sodium methanolate, or potassium methanolate, to produce glycerine and methyl or ethyl esters of the fatty acids. The glycerin is then separated from the biodiesel. Once the separation of glycerin and biodiesel is complete, the alcohol may be removed by distillation. The glycerin is generally neutralized with an acid and sent to storage as crude glycerin. Once separated from the glycerin, the biodiesel generally is purified by washing it gently with warm water (the methyl ester wash) to remove residual catalysts and/or soaps, dried, and sent to storage.

[0048] The present invention also contemplates blends of biodiesel and petroleum based diesel fuels. It will be appreciated by the skilled artisan that the amount of biodiesel and petroleum diesel present in the fuel composition of the present invention can and will vary depending upon the fuel's intended use. For example, the fuel composition may comprise from about 10% to about 40% by weight of biodiesel and from about 60% to about 90% by weight of the petroleum based diesel. In another embodiment, the fuel composition may comprise from about 20% to about 30% by weight of biodiesel and from about 70% to about 80% by weight of the petroleum based diesel. In yet another embodiment, the fuel composition comprises about 20% by weight of biodiesel and about 80% by weight of the petroleum based diesel, which is known as B20.

[0049] The concentration of antioxidant composition added to the fuel will vary depending on the source or composition of the fuel. The amount, for example, may range from about 5 ppm to about 2500 ppm. In other embodiments, the amount may range from about 20 to about 100 ppm, 100 to about 200 ppm, 200 to about 300 ppm, 300 to about 400 ppm, 400 to about 500 ppm, 500 to about 600 ppm, 600 to about 700 ppm, 700 to about 800 ppm, 800 to about 900 ppm, 900 to about 1000 ppm, 1000 to about 1100 ppm, 1100 to about 1200 ppm, 1200 to about 1300 ppm, 1300 to about 1400 ppm, 1400 to about 1500 ppm, 1500 to about 1600 ppm, 1600 to about 1700 ppm, 1700 to about 1800 ppm, 1800 to about 1900 ppm, 1900 ppm to about 2000 ppm, or greater than about 2000 ppm.

[0050] In addition, the concentration of antioxidant composition will also vary in accordance with the oxidative stability desired for the fuel. There are various methods generally known in the art to measure the oxidative stability of a fuel, including the Rancimat Method, the Oxidative Stability Index (OSI) Method, Active Oxygen Method (AOM), the Standard Test Method for Oxidation Stability of Distillate Fuel oil (ASTM D-2274). These methods may be utilized by a skilled artisan to formulate blends of antioxidants having a suitable concentration of each ingredient in order for the antioxidant blend to impart the desired oxidative stability for the fuel. For example, all oils and fats have a resistance to oxidation, which depends on the degree of saturation, natural or added antioxidants, prooxidants or prior abuse. Oxidation is slow until this resistance is overcome, at which point oxidation accelerates and becomes very rapid. The length of time before this rapid acceleration of oxidation is the measure of the resistance to oxidation and is commonly referred to as the induction period. The OSI Method measures this induction period. Another method used in the art to measure induction period is the Rancimat Method.

[0051] The stabilized fuel compositions may contain additional agents that enhance one or more characteristics of the fuel. Those skilled in the art will appreciate that the selection of the particular agent will vary considerably depending on the type of fuel in the composition and its intended use. In particular, these additives may be particularly beneficial when the fuel composition comprises a biodiesel and a petroleum based diesel. Suitable additives, for example, may include, but are not limited to, cetane improvers and/or ignition accelerator agents, corrosion inhibitors and/or metal deactivators, cold flow improvers, detergents, thermal stabilizers, antiwear agents, demulsifiers, and the like.

[0052] The stabilized fuel compositions of the invention may be used as automotive fuels (i.e., in automobiles, trucks, motorcycles, buses, water craft, lawn mowers, tractors, heavy equipment, small engines, and so forth). Furthermore, the stabilized fuel compositions of the invention may be used as heating fuels (i.e., used to heat homes, businesses, schools, and the like).

DEFINITIONS

[0053] To facilitate understanding of the invention, a number of terms and abbreviations as used herein are defined below: [0054] The term "AOM" stands for the Active Oxygen Method. The method measures the time (in hours) required for a sample of fat or oil to attain a predetermined peroxide value under the specific conditions of the test.

[0055] The term "B20" refers to a fuel composition having about 20% by weight biodiesel and about 80% by weight petroleum based diesel.

[0056] The terms "induction time" or "induction period" stand for the measure of the resistance to oxidation.

[0057] The term "IPV" stands for the "initial peroxide value" and may be expressed in Meq/kg or ppm.

[0058] As used herein, the terms "chelating agent," "chelator," "amine chelating agent," or "acidic chelating agent" refer to any compounds that will chelate metal cations present in biodiesel.

[0059] The term "Oxidative Stability" refers to the ability to slow down the oxidation of a fuel.

[0060] The term "OSI" stands for the Oil Stability Index. The method measures the induction time of a fuel.

[0061] The term "ppm" stands for parts per million.

[0062] The term "Rancimat" refers to a method that determines the oxidative stability of oil, biodiesel, lipids, etc. The method measures the induction time of a lipid material.

[0063] The term "yellow grease" as used herein refers to waste grease from restaurants and low-grade fats from rendering plants; yellow grease is a mixture of vegetable oils and animal fats.

[0064] As used throughout this application, references to compounds as having a specific number of carbon atoms (e.g. "C2-C10") refers to compounds for which the total number of carbon atoms in the molecule is in the range specified (e.g. 2-10 total carbons).

[0065] The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples that follow represent techniques discovered by the inventors to function well in the practice of the invention. Those of skill in the art should, however, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention, therefore all matter set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

EXAMPLES

[0066] The following examples illustrate various embodiments of the invention.

Example 1: Effectiveness of Phenol-Based Antioxidants to Stabilize Biodiesel

[0067] The ability of phenol-based antioxidants alone or with 2-tert- butylhydroquinone (TBHQ) to stabilize biodiesel was determined. The stability of the biodiesel was tested using the Rancimat EN 14112 method. For this, a stream of air is passed through a sample that is maintained at 110 ⁰C, and the effluent air from the sample is bubbled through a test vessel containing deionized water, whose conductivity is continuously monitored. As the biodiesel oxidizes, volatile organic acids are generated and become trapped in the water, thereby increasing its conductivity. A computer was used to monitor the conductivity and generate a plot of water conductivity vs. time. The Rancimat value is defined as the induction period (IP) in hours and mathematically represents the inflection point (second derivative) of the plot that reflects the maximum change in the oxidation rate. The higher the IP value, the more stable the biodiesel.

[0068] The biodiesel used was rapeseed methyl-ester biodiesel (RME;

Campa AG, Ochenfurt, Germany). TBHQ was used at 360 ppm (i.e., 36% at 1000 ppm) and the other phenol-based antioxidants were used at 200 ppm (i.e., 20%). Table 1 presents the IP values for each phenol-based antioxidant alone or in combination with TBHQ. TBHQ was the most effective biodiesel stabilizer and the addition of another phenol-based antioxidant had little additional stabilizing effect. Table 1. Activity of Phenol-Based Antioxidants ± TBHQ

Example 2: Effectiveness of a Chelator with or without TBHQ to Stabilize Biodiesel

[0069] Chelating agents may improve the effectiveness of antioxidants to stabilize biodiesel by removing metal ions. The ability of chelators alone or with TBHQ to stabilize RME biodiesel was also determined using the Rancimat method described in Example 1.

[0070] The chelators were used at 30 ppm (i.e., 3%) and TBHQ was used at 360 ppm (i.e., 36% at 1000 ppm). Table 2 presents the IP values for the chelators alone or in combination with TBHQ. None of the chelating agents alone significantly improved the stability of the biodiesel, and none of the chelating agents significantly increased the stabilizing activity of TBHQ.

Table 2. Activity of Chelators ± TBHQ

Example 3: Effectiveness of a Chelator and TBHQ to Stabilize Copper-Containing Biodiesel

[0071] To more readily detect the activity of a chelating agent and an antioxidant, the biodiesel was supplemented with copper ions. Accordingly, RME biodiesel was supplemented with 2.8 ppm Of Cu(II)OAc (i.e., 1 ppm Cu(II) ion). The ability of TBHQ alone or in combination of a chelator to stabilize such copper-containing biodiesel was determined using the Rancimat method essentially as described in Example 1. The chelators were used at 30 ppm (i.e., 3%) and TBHQ was used at 360 ppm (i.e., 36% at 1000 ppm).

[0072] Table 3 presents the IP values for TBHQ alone or TBHQ in combination with a chelating agent. TBHQ alone was not effective in stabilizing copper- containing biodiesel, and as shown above, chelators alone did not stabilize biodiesel. It was found, however, that the combinations of TBHQ and certain carboxylic acids were very effective in stabilizing the copper-containing biodiesel. In particular, the combinations of TBHQ/cithc acid or TBHQ/tartaric acid stabilized the biodiesel.

Table 3. Activity of TBHQ ± Chelator to Stabilize Copper-Containing Biodiesel

Condition IP (hr)

Control 1.11

TBHQ 1.57

TBHQ + Citric Acid 17.33

Control 2.26

TBHQ 3.58

TBHQ + Heavy Polyamine X 4.79

TBHQ + Thethylenetetramine 2.97

TBHQ + Succinic Acid 3.21

TBHQ + Sorbic Acid 5.39

TBHQ + DL-MaNc Acid 8.20

TBHQ + L(+)-Tartaric Acid 22.54

Example 4: Formulations Comprising Phenol-Based Antioxidants, Tartaric Acid, and Amine Chelating Agent

[0073] Formulations comprising TBHQ, tartaric acid, and an amine chelator were generated. The formulations comprised 20% TBHQ, 3% tartaric acid, 5% of an amine chelator, and a filler (e.g., propylene glycol). They were tested for their ability to stabilize RME biodiesel essentially as described in Example 1. The formulations were mixed with the biodiesel at 500 ppm. As shown in Table 4, all of the formulations were effective at stabilizing biodiesel. Table 4. Stabilizin Activit .

Example 5: Formulations Comprising At Least One Phenolic Antioxidant and At Least One Chelating Agent

[0074] Formulations were prepared that comprised combinations of phenolic antioxidants and chelating agents. Table 5 presents the compositions of formulations comprising TBHQ, 2,6-di-tert-butyl phenyl (DTBP), tetraethylenepentamine (TEPA), and tartaric acid (TTA) (with the balance of the formulation being a filler). The formulations were mixed with the RME biodiesel at 500 ppm. Table 5 also presents the IP values of these formulations. Formulations 3 and 5 were most effective.

Table 5. Stabilization of RME Biodiesel.

[0075] Table 6 presents the compositions of formulations comprising

TBHQ, ethoxyquin (EQ), heavy polyamine X (HPX), and TTA, as well as their IP values for stabilizing RME biodiesel. Despite the fact that all formulations were quite efficacious, however, formulations 6 and 8 showed the highest Rancimat values and thus, effectively stabilized the biodiesel.

Table 6. Stabilization of RME Biodiesel.

[0076] Table 7 presents the compositions of formulations comprising EQ,

TBHQ, 1 -naphthol (AN), and TTA, as well their IP values for stabilizing RME biodiesel. Formulations comprising 20% TBHQ were the most effective.

Table 7. Stabilization of RME Biodiesel.

Example 6: Stabilization of Distilled RME Biodiesel

[0077] The ability of various formulations to stabilize distilled biodiesel was also tested. Table 8 presents the composition of formulations comprising combinations of HPX, TBHQ, and TTA (the balance of each formulation was a filler), the inclusion rates, and the IP values for distilled RME (initial peroxide value (IPV) = 4.5 meq/kg biodiesel). For comparison, the stabilizing activity of 2,6-di-tert-butyl-4-methylphenol (also known as butylated hydroxytoluene, BHT) was also tested.

Table 8. Stabilization of Distilled RME Biodiesel.

[0078] Table 9 presents the composition of formulations comprising combinations of AN, TBHQ, EQ, and TTA, as well their IP values for stabilizing distilled RME biodiesel.

Table 9. Stabilization of Distilled RME Biodiesel.

Example 7: Effectiveness of Additional Formulations

[0079] Additional amines and phenolic antioxidants were tested in formulations comprising tartaric acid for their ability to stabilize RME biodiesel or distilled RME (DRME) biodiesel. Table 10 presents the compositions of formulations comprising combinations of N,N'-diphenyl-1 ,4-phenylenediamine (DPDA), TTA, and either 2, 2'-methylenebis(6-tert-butyl-4-methyl-phenol), 2,2'-methylenebis(6-tert-butyl-4- ethyl phenol), or 4,4'-methylenebis(2,6-di-tert-butyl phenol), as well as IP values. These formulations did not significantly effect the stabilization of undistilled RME biodiesel, but they were quite effective in their stabilization of distilled RME biodiesel.

Table 10. Biodiesel Stabilization.

[0080] Table 11 presents results for formulations comprising combinations of TBHQ, 4,4'-methylenebis(2,6-di-tert-butyl phenol) (44DTBP), TTA, and either N₁N'- diphenyl-1 ,4-phenylenediamine (DPDA) or p-phenylenediamine (PPDA). The formulations were used at 1000 ppm inclusion rate. Formulations comprising DPDA were much more effective at stabilizing distilled RME biodiesel that formulations comprising PPDA.

Table 11. Biodiesel Stabilization.

Example 8: Formulations Comprising an Ethylene Amine

[0081] Formulations comprising an ethylene amine were tested for their ability to stabilize RME biodiesel and soybean methyl ester (SME) biodiesel. The formulations optionally contained benzyl acetate (BA), citric acid (CA), and propylene glycol (Pgyl).

[0082] Table 12 presents the compositions of the formulations comprising pentaethylenehexamine (PEHA), tetraethylenepentamine (TEPA), and/or triethylenetetramine (3ETA), as well as IP values. Formulations comprising two or more ethylene amines were most effective at stabilizing RME and SME biodiesel.

Table 12. Biodiesel stabilization.

[0083] Formulations comprising both PEHA and TEPA in combination with butylated hydroxytoluene (BHT), benzyl acetate (BA), and/or 2-tert-butyl-phenol (TBP) were prepared. Table 13 presents the compositions of the formulations, as well as IP values. Formulations comprising the ethylene amines effectively stabilized the biodiesel.

Table 13. Biodiesel stabilization.

Example 9: Formulations Comprising Propyl Gallate

[0084] Formulations comprising the antioxidant propyl gallate (PG) in addition to PEHA and TBP were prepared and tested. Table 14 presents the compositions of the formulations and the IP values for SME biodiesel (IPV = 13.835). The formulations comprising PG and TBP effectively stabilized SME biodiesel.

Table 14. Biodiesel stabilization.

Example 10: Formulations Comprising an Aromatic Solvent

[0085] Formulations comprising the aromatic solvent Aromatic 150

(AR150) were tested. Table 15 presents the compositions of the formulations (used at 1000 ppm) comprising combinations of TEPA, PG, TBP, AR150, and BAYNOX^® Plus [i.e., 2,2'-methylene-bis(6-tert-butyl-4-methylphenol)], a commercial biodiesel stabilizer, as well as IP values for RME and SME biodiesel. Addition of Aromatic 150 and the stabilizer allowed the use of lower concentrations of TEPA while still stabilizing RME and SME biodiesel.

Table 15. Biodiesel stabilization

Example 11: Formulations Comprising Citric Acid

[0086] Formulations comprising TEPA, PG, TBP, and AR150 were supplemented with citric acid (CA) and tested for their ability to stabilize SME (Table 16) or RME (Table 17). The tables present the compositions of these formulations, the dose rate, and the IP values for each type of biodiesel.

Table 16. SME stabilization.

[0087] The formulation comprising 75% TEPA was tested further with and without CA. Table 18 presents the compositions of these formulations, the dose rate, and the IP values for RME biodiesel (IPV = 4.315 ppm).

Table 18. Activity of Formulations Comprising TEPA.

Table 18. Activit of Formulations Com risin TEPA.

Example 12: Activity of Optimized Formulation

[0088] The data presented above indicates that combinations of pentaethylenehexaamine (PEHA), propyl gallate (PG), 2-tert-butylphenol (TBP), and Aromatic 150 (AR150) were consistently effective at increasing the oxidative stability of biodiesel.

[0089] Table 19 presents the effectiveness of several formulations comprising different concentrations of PEHA to stabilize SME or RME.

Table 19. Activity of Formulations Comprisinc PEHA

[0090] A formulation comprising 75% PEHA, 5% PG, 10% TBP, and 10%

AR150 was used at 100% or diluted to 80%. Various application rates of each formulation were tested for their ability to stabilize RME or SME (IPV = 7.196 ppm). Table 20 presents the dose response results.

Table 20. PEHA Formulations.

Example 13: Stabilization of Various Biodiesel Preparations

[0091] The formulation comprising 75% TEPA, 5% PG, 10% TBP, and

10% AR150 was tested for it ability to stabilize biodiesel from a variety of sources having different starting initial peroxide values. Table 22 presents the IP values at two dose rates (in ppm) for the different biodiesel preparations. The formulation at 500 ppm significantly stabilized each biodiesel solution.

Table 21. Stabilization of Different Biodiesel Preparations.

Example 14: Chelating Properties of Various Formulations

[0092] To determine the chelating efficacy of several formulations, SME was supplemented with 1 ppm Cu from Cu(II) acetate or 1 ppm Fe from Fe(NH₄)₂(SO₄)₂. The chelating activity of the antioxidant formulation comprising 75% TEPA, 5% PG, 10% TBP, and 10% AR150 was compared to those of BHT alone, TBHQ alone, and a mixture of 30% TBHQ and 1.5% citric acid. Each formulation was used at a dose of 200 ppm to stabilize SME with no added metal (IPV = 6.544 ppm), SME + Cu, or SME + Fe. Table 23 presents the results. The antioxidant formulation comprising TEPA stabilized the metal-supplemented biodiesel.

Table 22. Stabilization of Metal-Containin Biodiesel

[0093] The chelating properties of the antioxidant formulation comprising

75% TEPA, 5% PG, 10% TBP, and 10% AR150 was analyzed further. SME was supplemented with 1 ppm of metal from the following sources: Cu(II)OAC, Fe(II)OAc, Mn(II)OAc, or Co(II)OAc. The antioxidant formulation was used at 200 ppm. As shown in Table 24, the antioxidant formulation (AOX) increased the oxidative stability of each biodiesel preparation.

Table 23. Stabilization of Metal-Containin Biodiesel

Example 15: Stabilization Monitored with Active Oxygen Method (AOM)

[0094] The ability of the TEPA comprising formulation (as detailed above) to stabilize RME or SME was monitored with the AOM. This method measures peroxide formed by reaction of active oxygen with the fatty acid esters in biodiesel. The AOX formulation was used at 200 ppm. Table 24 presents the results. The AOX formulation decreased the formation of peroxides in both types of biodiesel.

Table 24. Peroxide Formation

RME SME

Control + AOX Control + AOX

IPV 6.6 6.6 8.9 8.9

20 hr 314.2 45.2 234.0 145.5

Claims

CLAIMSWhat is claimed is:

1. A composition comprising at least one ethylene amine and at least one phenolic antioxidant.

2. The composition of claim 1 , wherein the ethylene amine is selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aminoethylpiperazine, and heavy polyamine X.

3. The composition of claim 1 , wherein the ethylene amine is tetraethylenepentamine or pentaethylenehexamine.

4. The composition of claim 1 , wherein the phenolic antioxidant is selected from the group consisting of alpha naphthol, butylated hydroxyanisole, butylated hydroxytoluene, ethoxyquin, gallic acid, dodecyl gallate, octyl gallate, propyl gallate, pyrogallol, 2-tert-butylphenol, 2,6-di-tert-butylphenol, 4,6-di-tert- butylphenol, 2,4,6-tri-tert-butylphenol, 2,6-diisopropylphenol, 4-sec-butyl-2,6- di-tert-butylphenol, and 2-tert-butylhydroquinone.

5. The composition of claim 1 , wherein the phenolic antioxidant comprises propyl gallate and 2-tert-butylphenol.

6. The composition of claim 1 , further comprising an aromatic solvent.

7. The composition of claim 6, wherein the aromatic solvent is an aromatic naphtha solvent.

8. The composition of claim 7, wherein the composition comprises from about 50% to about 80% by weight of tetraethylenepentamine or pentaethylenehexamine, from about 0% to about 10% by weight propyl gallate, from about 5% to about 20% by weight of 2-tert-butylphenol, and from about 5% to about 30% by weight of the aromatic naphtha solvent.

9. The composition of claim 1 , further comprising an acidic chelating agent selected from the group consisting of a dicarboxylic acid and a tricarboxylic acid.

10. The composition of claim 1 , further comprising a detergent selected from the group consisting of a polyisobutylene succinimide, a polyisobutylene succinic anhydride or derivative thereof, a polyether compound, a polyether-polyol compound, and an epoxylated ester compound.

11. The composition of claim 1 , further comprising a biodiesel solution.

12. The composition of claim 11 , wherein the composition contains from about 20 ppm to about 2000 ppm of the composition of the composition of claim 1.

13. The composition of claim 11 , wherein the biodiesel solution is produced from a source selected from the group consisting of soybean oil, yellow grease, corn oil, rapeseed oil, coconut oil, peanut oil, palm oil, fish oil, marine oil, cottonseed oil, mustard seed oil, camelina oil, jojoba oil, hemp oil, tallow, poultry fat, lard, safflower oil, jatropha oil, algae oil, and sunflower oil.

14. The composition of claim 11 , further comprising an additive selected from the group consisting of cetane improvers, ignition accelerators, metal deactivators, corrosion inhibitors, thermal stabilizers, detergents, antiwear agents, and demulsifiers.

15. The composition of claim 11 , further comprising a petroleum based diesel fuel.

16. The composition of claim 15, wherein the composition comprises from about 20% to about 30% by weight of the biodiesel solution and from about 70% to about 80% by weight of the petroleum based diesel fuel.

17. A composition consisting essentially of at least one ethylene amine, at least one phenolic antioxidant, and an aromatic solvent.

18. The composition of claim 17, wherein the composition consists of about 75% by weight of tetraethylenepentamine, about 5% by weight of propyl gallate, about 10% by weight of 2-tert-butylphenol, and about 10% by weight of aromatic naphtha solvent.

19. The composition of claim 17, wherein the composition consists of about 75% by weight of pentaethylenehexamine, about 5% by weight of propyl gallate, about 10% by weight of 2-tert-butylphenol, and about 10% by weight of aromatic naphtha solvent.

20. A composition comprising at least one phenolic antioxidant and a hydroxy dicarboxylic acid.

21. The composition of claim 20, wherein the phenolic antioxidant is selected from the group consisting of alpha naphthol, butylated hydroxyanisole, butylated hydroxytoluene, ethoxyquin, gallic acid, dodecyl gallate, octyl gallate, propyl gallate, pyrogallol, 2-tert-butylphenol, 2,6-di-tert-butylphenol, 4,6-di-tert- butylphenol, 2,4,6-tri-tert-butylphenol, 2,6-diisopropylphenol, 4-sec-butyl-2,6- di-tert-butylphenol, and 2-tert-butylhydroquinone.

22. The composition of claim 20, wherein the antioxidant is 2-tert- butylhydroquinone or a 2-tert-butylhydroquinone isomer.

23. The composition of claim 20, wherein the hydroxy dicarboxylic acid is 2,3- dihydroxybutanedioic acid.

24. The composition of claim 20, further comprising a solvent selected from the group consisting of glycols, glycol ethers, glycol ether esters, alcohols, ketones, amides, and ethers.

25. The composition of claim 24, wherein the solvent comprises propylene glycol and octanol.

26. The composition of claim 25, wherein the composition comprises from about 5% to about 40% by weight of 2-tert-butylhydroquinone, from about 0.5% to about 5% by weight of 2,3-dihydroxybutanedioic acid, from about 1 % to about 10% by weight of octanol; and from about 45% to about 93.5% by weight of propylene glycol.

27. The composition of claim 20, further comprising an amine.

28. The composition of claim 27, wherein the amine is selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aminoethylpiperazine, heavy polyamine X, N,N'-di-sec-butyl-1 ,4-phenylenediamine, 2-(2- aminoethylamino)ethanol, ethylenediaminetetraacetic acid, N-(2- hydroxyethyl)ethylene diamine-N,N',N'-triacetic acid, N,N,N',N'-tetraacetic acid, ethylenediamine-N,N'diacetic acid, diethylenethaminepentaacetic acid, and trans-1 ,2-diaminocyclohexane.

29. The composition of claim 20, further comprising a detergent selected from the group consisting of a polyisobutylene succinimide, a polyisobutylene succinic anhydride or derivative thereof, a polyether compound, a polyether-polyol compound, and an epoxylated ester compound.

30. The composition of claim 20, further comprising a biodiesel solution.

31. The composition of claim 30, wherein the composition contains from about 20 ppm to about 2000 ppm of the composition of the composition of claim 20.

32. The composition of claim 30, wherein the biodiesel solution is produced from a source selected from the group consisting of soybean oil, yellow grease, corn oil, rapeseed oil, coconut oil, peanut oil, palm oil, fish oil, marine oil, cottonseed oil, mustard seed oil, camelina oil, jojoba oil, hemp oil, tallow, poultry fat, lard, safflower oil, jatropha oil, algae oil, and sunflower oil.

33. The composition of claim 30, further comprising an additive selected from the group consisting of cetane improvers, ignition accelerators, metal deactivators, corrosion inhibitors, thermal stabilizers, detergents, antiwear agents, and demulsifiers.

34. The composition of claim 30, further comprising a petroleum based diesel fuel.

35. The composition of claim 34, wherein the composition comprises from about 20% to about 30% by weight of the biodiesel solution and from about 70% to about 80% by weight of the petroleum based diesel fuel.

36. A composition consisting essentially of at least one phenolic antioxidant and 2,3-dihydroxybutanedioic acid.

37. The composition of claim 36, wherein the phenolic antioxidant is 2-tert- butylhydroquinone.

38. A composition comprising 2-tert-butylhydroquinone, 2,3-dihydroxybutanedioic acid, and an amine.

39. The composition of claim 38, further comprising at least one phenolic antioxidant other than 2-tert-butylhydroquinone selected from the group consisting of alpha naphthol, butylated hydroxyanisole, butylated hydroxytoluene, ethoxyquin, gallic acid, dodecyl gallate, octyl gallate, propyl gallate, pyrogallol, 2-tert-butylphenol, 2,6-di-tert-butylphenol, 4,6-di-tert- butylphenol, 2,4,6-tri-tert-butylphenol, 2,6-diisopropylphenol, and 4-sec-butyl- 2,6-di-tert-butylphenol.

40. The composition of claim 38 or claim 39, further comprising a solvent selected from the group consisting of glycols, glycol ethers, glycol ether esters, alcohols, ketones, amides, and ethers.

41. The composition of claim 40, wherein the solvent comprises octanol and propylene glycol.

42. The composition of claim 41 , wherein the composition comprises from about 5% to about 40% by weight of 2-tert-butylhydroquinone; from about 0.5% to about 5% by weight of 2,3-dihydroxybutanedioic acid; from about 5% to about 20% by weight of phenolic antioxidant other than 2-tert-butylhydroquinone; from about 5% to about 40% by weight of amine; from about 1 % to about 10% by weight of octanol; and from about 1 % to about 83.5% by weight of propylene glycol.

43. The composition of claim 38 or claim 39, wherein the amine is selected from the group consisting of ethylenediamine, diethylenethamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aminoethylpiperazine, heavy polyamine X, N,N'-di-sec-butyl-1 ,4- phenylenediamine, 2-(2-aminoethylamino)ethanol, ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylene diamine-N,N',N'-thacetic acid, N, N, N', N'- tetraacetic acid, ethylenediamine-N,N'diacetic acid, diethylenethaminepentaacetic acid, and trans-1 ,2-diaminocyclohexane.

44. The composition of claim 38 or claim 39, further comprising a detergent selected from the group consisting of a polyisobutylene succinimide, a polyisobutylene succinic anhydride or derivative thereof, a polyether compound, a polyether-polyol compound, and an epoxylated ester compound.

45. The composition of claim 38 or claim 39, further comprising a biodiesel solution.

46. The composition of claim 45, wherein the composition contains from about 20 ppm to about 2000 ppm of the composition of the composition of claim 38 or claim 39.

47. The composition of claim 45, wherein the biodiesel solution is produced from a source selected from the group consisting of soybean oil, yellow grease, corn oil, rapeseed oil, coconut oil, peanut oil, palm oil, fish oil, marine oil, cottonseed oil, mustard seed oil, camelina oil, jojoba oil, hemp oil, tallow, poultry fat, lard, safflower oil, jatropha oil, algae oil, and sunflower oil.

48. The composition of claim 45, further comprising an additive selected from the group consisting of cetane improvers, ignition accelerators, metal deactivators, corrosion inhibitors, thermal stabilizers, detergents, antiwear agents, and demulsifiers.

49. The composition of claim 45, further comprising a petroleum based diesel fuel.

50. The composition of claim 49, wherein the composition comprises from about 20% to about 30% by weight of the biodiesel solution and from about 70% to about 80% by weight of the petroleum based diesel fuel.

51. A composition consisting essentially of a phenolic antioxidant, 2,3- dihydroxybutanedioic acid, and an amine.

52. The composition of claim 51 , wherein phenolic antioxidant is 2-tert- butylhydroquinone.

53. A method for increasing the oxidative stability of a fuel composition, the method comprising contacting the fuel composition with an antioxidant composition of claim 1 , claim 20, claim 38, or claim 39.

54. The method composition of claim 53, wherein the concentration of the antioxidant composition is from about 20 ppm to about 2000 ppm.

55. The method of claim 53, wherein the fuel composition comprises a biodiesel solution.

56. The method of claim 55, wherein the biodiesel solution is produced from a source selected from the group consisting of soybean oil, yellow grease, corn oil, rapeseed oil, coconut oil, peanut oil, palm oil, fish oil, marine oil, cottonseed oil, mustard seed oil, camelina oil, jojoba oil, hemp oil, tallow, poultry fat, lard, safflower oil, jatropha oil, algae oil, and sunflower oil.

57. The method of claim 55, wherein the fuel composition further comprises a petroleum based diesel fuel.

58. The method of claim 57, wherein the fuel composition comprises from about 20% to about 30% by weight of the biodiesel solution and from about 70% to about 80% by weight of the petroleum based diesel fuel.