BIODIESEL ET CARBURANTS MELANGES AU BIODIESEL

BIODIESEL AND BIODIESEL BLEND FUELS

Abrégé français

La présente invention concerne des compositions de carburants comprenant des combinaisons synergiques d'un biodiesel ou d'un mélange comprenant du biodiesel, d'un antioxydant comprenant un mélange d'au moins un diphénol et d'au moins un phénol stériquement encombré, et d'un amélioreur de cétane. Les compositions de carburants décrites ici présentent une combinaison unique d'une stabilité améliorée à l'oxydation et d'une meilleure qualité d'allumage.

Abrégé anglais

biodiesel, diesel, blend, cetane improver, antioxidant, dihydroxybenzene, 2,6-di-tert-butyl-alpha-dimethylam?no-p-cresol, 2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl nitrate, ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl nitrate, isobutyt nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate, isoamyl nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-octyl nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate, cyclopentylnitrate, cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate, 1 -methoxypropyl-2-n?trate, 1 - ethoxpropyl-2 nitrate, 1 -isopropoxy-butyl nitrate, 1-ethoxylbutyl nitrate, nitrate, diphenol, hydroqumone, tert-butylhydroqumone, 2-tert- butyl-1,4-hydroqu?none, 2,5-ditert-butyl-1,4-hydroqu?none, methylhydroquinone, 2,5-di-tert octylhydroquinone, benzenediol, dihydroxybenzene, Resorcinol, Pyrocatechol, sterically hindered phenol, "2,6-di-tert-butylphenol", "2,4-di-tert-butylphenor, 6-d?-tert- butyl-4-methylphenol, 2-tert-butylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tertbutyl-4-d?methylam?nomethylphenol, ethanox

Revendications

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CLAIMS:
1. A fuel composition comprising:
(a) between about 0.0 1 % to about 1% by volume of a cetane
improver;
(b) a biodiesel blend comprising about 2% to about 98% by
volume of a biodiesel and about 2% to about 98% by volume of a petroleum
distillate; and
(c) an antioxidant comprising a mixture of a diphenol and a
sterically hindered phenol, wherein
(1) the amount of the antioxidant is (i) between about 20
milligrams per kilogram to about 10,000 milligrams per kilogram of the
biodiesel blend, or (ii) is between about 16 milligrams per liter to about
8,000
milligrams per liter of the biodiesel blend, and
(2) wherein the volumetric ratio of the diphenol to the
sterically hindered phenol is between about 0.01:1 to about 10:1.
2. The fuel composition of claim 1, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl
nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate, and mixtures thereof;

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(b) the biodiesel blend comprises (1) between about 2% to about
98% by volume of a biodiesel comprising between about 50% to about 99% by
weight of methyl, ethyl, and propyl esters of saturated and unsaturated fatty
acids, and (2) between about 2% to about 98% by volume of a petroleum
distillate;
(c) the diphenol is selected from the group consisting of
hydroquinone, tert-butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-
tert-butyl-1,4-hydroquinone, methylhydroquinone, 2,5-di-tert.-
octylhydroquinone, and mixtures thereof; and
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, 2, 6-di-tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof.
3. The fuel composition of claim 1, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl
nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropy1-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate and mixtures thereof;
(b) the biodiesel blend comprises (1) between about 2% to about
98% by volume of a biodiesel formed by transesterifying an alcohol with a
composition selected from the group consisting of soybean oil, rapeseed oil,

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palm oil, canola oil, sunflower oil, olive oil, corn oil, coconut oil,
jatropha oil,
tallow oil, yellow grease animal fats, used cooking oil, and mixtures thereof,
and
(2) between about 2% to about 98% of a petroleum distillate;
(c) the diphenol is selected from the group consisting of
hydroquinone, tert-butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-
tert-butyl-1,4-hydroquinone, methylhydroquinone, 2,5-di-tert.-
octylhydroquinone and mixtures thereof; and
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, 2, 6-di-tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof.
4. The fuel composition of claim 1, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl
nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate and mixtures thereof;
(b) the biodiesel blend comprises (1) between about 2% to about
98% by volume of a biodiesel comprising a fatty acid ester selected from the
group consisting of rapeseed methyl ester, a canola methyl ester, a soybean
methyl ester, a corn oil methyl ester, or a mixture thereof, and (2) between
about
2% to about 98% by volume of a diesel;

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(c) the diphenol is selected from the group consisting of
hydroquinone, tert-butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-
tert-butyl-1,4-hydroquinone, methylhydroquinone, 2,5-di-tert.-
octylhydroquinone, and mixtures thereof; and
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, 2, 6-di-tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof.
5. The fuel composition of claim 1, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl
nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate and mixtures thereof;
(b) the biodiesel blend comprises (1) between about 2% to about
98% by volume of a biodiesel comprising a fatty acid ester selected from the
group consisting of rapeseed methyl ester, a canola methyl ester, a soybean
methyl ester, a corn oil methyl ester, or a mixture thereof, and (2) between
about
2% to about 98% by volume of a diesel; and
(c) the diphenol and sterically hindered phenol are selected,
respectively, from a compound of formula (I) and a compound of formula (II):

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<IMG>
wherein R1 and R3 are H or a tert-butyl group, and R2 is H, CH3, a tert-butyl
group or -CH2-N(CH3)2.
6. The fuel composition of claim 1, wherein:
(a) the fuel composition contains about 0.1% to about 0.35% by
volume of a cetane improver;
(b) the biodiesel blend comprises (1) about 5% to about 30% by
volume of a biodiesel comprising a fatty acid ester selected from the group
consisting of rapeseed methyl ester, a canola methyl ester, a soybean methyl
ester, a corn oil methyl ester, or a mixture thereof, and (2) about 70 to
about 90%
by volume of a diesel;
(c) the diphenol is selected from the group consisting of tert-
butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-tert-butyl-1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and
mixtures thereof;
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-
tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof;
(e) the fuel composition contains about 100 milligrams of
antioxidant per liter of the biodiesel blend to about 500 milligrams of
antioxidant
per liter of the biodiesel blend; and

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(f) the volumetric ratio of the diphenol to the sterically hindered phenol is
between about 0.5:1 to about 1.5:1.
7. The fuel composition of claim 1, wherein:
(a) the fuel composition contains about 0.1% to about 0.35% by
volume of a cetane improver;
(b) the biodiesel blend comprises (1) about 5% to about 30% by
volume of a biodiesel comprising a fatty acid ester selected from the group
consisting of rapeseed methyl ester, a canola methyl ester, a soybean methyl
ester, a corn oil methyl ester, or a mixture thereof, and (2) about 70 to
about 95%
by volume of a diesel; and
(c) the diphenol is selected from the group consisting of tert-
butylhydroquinone, 2-tert-butyl- 1,4-hydroquinone, 2,5-di-tert-butyl-1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and
mixtures thereof;
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-
tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof;
(e) the fuel composition contains about 200 milligrams of
antioxidant per liter of the biodiesel blend to about 400 milligrams of
antioxidant
per liter of the biodiesel blend; and
(f) the volumetric ratio of the diphenol to the sterically hindered
phenol is between about 0.75:1 to about 1.:1.
8. The fuel composition of claim 1, wherein:
(a) the fuel composition contains about 0.1% to about 0.35% by
volume of a cetane improver;

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(b) the biodiesel blend comprises (1) about 5% to about 15% by
volume of a biodiesel comprising between about 50% to about 90% by weight of
methyl, ethyl, and propyl esters of saturated and unsaturated fatty acids, and
(2)
about 85 to about 95% by volume of a diesel;
(c) the diphenol is selected from the group consisting of tert-
butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-tert-butyl-1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and
mixtures thereof;
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-
tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof;
(e) the fuel composition contains about 200 milligrams of
antioxidant per liter of the biodiesel blend to about 400 milligrams of
antioxidant
per liter of the biodiesel blend; and
(f) the volumetric ratio of the diphenol to the sterically hindered
phenol is between about 0.75:1 to about 1.:1.
9. The fuel composition of claim 1, wherein the fuel composition
further comprises a composition selected from the group consisting of an
aromatic amine antioxidant and a performance additive.
10. The fuel composition of claim 1, wherein the fuel composition
comprises:
(a) about 0.3% by volume of 2-ethylhexyl nitrate;
(b) a biodiesel blend comprising about 5% by volume of a
biodiesel and about 95% by volume of a diesel; and

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(c) about 400 milligrams per liter of the biodiesel blend of an
antioxidant comprising a mixture of 2-tert-butyl- 1, 4-hydroquinone and a
sterically hindered phenol, wherein the volumetric ratio of 2-tert-butyl- 1, 4-
hydroquinone to the sterically hindered phenol is about 1: 1.
11. The fuel composition of claim 1, wherein the fuel composition
comprises:
(a) about 0.3% by volume of 2-ethylhexyl nitrate;
(b) a biodiesel blend comprising about 5% by volume of a
biodiesel and about 95% by volume of a diesel; and
(c) about 400 milligrams per liter of the biodiesel blend of an
antioxidant comprising a mixture of 2-tert-butyl- 1, 4-hydroquinone and a
sterically hindered phenol selected from the group consisting of Ethanox®
4703
and Ethanox® 4733, wherein the volumetric ratio of 2-tert-butyl-1, 4-
hydroquinone to the sterically hindered phenol is about 1:1.
12. The fuel composition of claim 11, wherein the biodiesel
comprises soybean methyl ester.
13. A fuel composition comprising:
(a) between about 0.01% to about 1% by volume of a cetane
improver;
(b) a biodiesel comprising between about 50% to about 99% by
weight of methyl, ethyl, and propyl esters of saturated and unsaturated fatty
acids; and
(c) an antioxidant comprising a mixture of a diphenol and a
sterically hindered phenol, wherein
(1) the amount of the antioxidant is (i) between about 20
milligrams per kilogram to about 10,000 milligrams per kilogram of the

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biodiesel, or (ii) is between about 16 milligrams per liter to about 8,000
milligrams per liter of the biodiesel, and
(2) wherein the volumetric ratio of the diphenol to the
sterically hindered phenol is between about 0.01:1 to about 10:1.
14. The fuel composition of claim 13, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl
nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate and mixtures thereof;
(b) the biodiesel is formed by transesterifying an alcohol with a
composition selected from the group consisting of soybean oil, rapeseed oil,
palm oil, canola oil, sunflower oil, olive oil, corn oil, tallow oil, coconut
oil,
jatropha oil, yellow grease animal fats, used cooking oil, and mixtures
thereof;
(c) the diphenol is selected from the group consisting of
hydroquinone, tert-butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-
tert-butyl-1, 4-hydroquinone, methylhydroquinone, 2, 5-di-tert. -
octylhydroquinone, and mixtures thereof; and
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, 2, 6-di-tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof.

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15. The fuel composition of claim 13, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl
nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate and mixtures thereof;
(b) the biodiesel comprises a fatty acid ester selected from the
group consisting of rapeseed methyl ester, a canola methyl ester, a soybean
methyl ester, a corn oil methyl ester, and mixtures thereof;
(c) the diphenol is selected from the group consisting of
hydroquinone, tert-butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-
tert-butyl-1,4-hydroquinone, methylhydroquinone, 2,5-di-tert.-
octylhydroquinone, and mixtures thereof; and
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, 2, 6-di-tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof.
16. the fuel composition of claim 13, wherein:
(a) the cetane improver is selected from the group consisting of
2-ethylhexyl nitrate, cyclohexyl nitrate, di-tert-butyl peroxide, methyl
nitrate,
ethyl nitrate, n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate,
isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate, n-amyl nitrate,
isoamyl

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nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate, n-hexyl nitrate, 2-
ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl nitrate, sec-
octyl
nitrate, n-nonyl nitrate, n-decyl nitrate, n-dodecyl nitrate,
cyclopentylnitrate,
cyclohexylnitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate,
1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-isopropoxy-butyl
nitrate,
1-ethoxylbutyl nitrate and mixtures thereof;
(b) the biodiesel comprises a fatty acid ester selected from the
group consisting of rapeseed methyl ester, a canola methyl ester, a soybean
methyl ester, a corn oil methyl ester, and mixtures thereof; and
(c) the diphenol and sterically hindered phenol are selected,
respectively, from a compound of formula (I) and a compound of formula (II):
<IMG>
wherein R1 and R3 are H or a tert-butyl group, and R2 is H, CH3, a tert-butyl
group or -CH2-N(CH3)2.
17. The fuel composition of claim 13, wherein:
(a) the fuel composition contains about 0.1% to about 0.35% by
volume of a cetane improver;
(b) the biodiesel comprises a fatty acid ester selected from the
group consisting of rapeseed methyl ester, a canola methyl ester, a soybean
methyl ester, a corn oil methyl ester, and mixtures thereof;
(c) the diphenol is selected from the group consisting of tert-
butylhydroquinone, 2-tert-butyl- 1,4-hydroquinone, 2,5-di-tert-butyl-1,4-

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hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and
mixtures thereof;
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-
tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof;
(e) the fuel composition contains about 100 milligrams of antioxidant per
liter
of the biodiesel to about 500 milligrams of antioxidant per liter of the
biodiesel;
and
(f) the volumetric ratio of the diphenol to the sterically
hindered phenol is between about 0.5:1 to about 1.5:1.
18. The fuel composition of claim 13, wherein:
(a) the fuel composition contains about 0.1% to about 0.35% by
volume of a cetane improver;
(b) the biodiesel comprises a fatty acid ester selected from the
group consisting of rapeseed methyl ester, a canola methyl ester, a soybean
methyl ester, a corn oil methyl ester, and mixtures thereof;
(c) the diphenol is selected from the group consisting of tert-
butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-tert-butyl-1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and
mixtures thereof;
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-
tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof;

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(e) the fuel composition contains about 400 milligrams of
antioxidant per liter of the biodiesel; and
(f) the volumetric ratio of the diphenol to the sterically hindered
phenol is between about 0.75:1 to about 1.:1.
19. The fuel composition of claim 13, wherein:
(a) the fuel composition contains about 0.1% to about 0.35% by
volume of a cetane improver;
(b) the biodiesel comprises about 50% to about 99% by weight
of methyl, ethyl, and propyl esters of saturated and unsaturated fatty acids;
(c) the diphenol is selected from the group consisting of tert-
butylhydroquinone, 2-tert-butyl- 1,4-hydroquinone, 2,5-di-tert-butyl- 1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and
mixtures thereof;
(d) the sterically hindered phenol is selected from the group
consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-
butyl-
4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-
tert-
butyl-4-dimethylaminomethylphenol, and mixtures thereof;
(e) the fuel composition contains about 400 milligrams of
antioxidant per liter of the biodiesel; and
(f) the volumetric ratio of the diphenol to the sterically
hindered phenol is between about 0.75:1 to about 1:1.
20. The fuel composition of claim 13, wherein the fuel composition
further comprises a composition selected from the group consisting of an
aromatic amine antioxidant and a performance additive.

Description

CA 02767928 2012-01-11
WO 2011/014424 PCT/US2010/043039
-1-
BIODIESEL AND BIODIESEL BLEND FUELS
FIELD OF THE INVENTION
[001] The invention provides fuel compositions comprising synergistic
combinations of a biodiesel or biodiesel blend, an antioxidant comprising a
mixture of at least one diphenol and at least one sterically hindered phenol,
and a
cetane improver.
BACKGROUND OF THE INVENTION
[002] Biodiesel is the name for a variety of ester-based oxygenated fuels
made from vegetable oils, fats, greases, or other sources of triglycerides.
Biodiesel is a nontoxic and biodegradable blendstock which may be blended
with petroleum diesel provided relevant specifications are met. Blends of
biodiesel with petroleum diesel can substantially reduce the emission levels
and
toxicity of diesel exhaust. Biodiesel has been designated as an alternative
fuel by
the United States Department of Energy and the United States Department of
Transportation, and is registered with the United States Environmental
Protection Agency as a fuel and fuel additive.
[003] Biodiesel fuels typically contain unsaturated fatty acid esters that can
easily oxidize in the presence of oxygen, especially if UV light, and/or trace
metals are also present. The products formed from this oxidation give rise to
sediment and gum formation within the fuel that can lead to corrosion and
plugging of filters, pumps and fuel injectors which utilize fuel containing
biodiesel.
[004] While antioxidants such as sterically-hindered phenols have been used
in an effort to stabilize biodiesels, there remains a need for a biodiesel
composition that has both improved oxidation stability and ignition quality
that
reduces or eliminates gum formation within the fuel, and that reduces or

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eliminates corrosion and plugging of filters, vehicular injection pumps and
fuel
injectors.
SUMMARY OF THE INVENTION
[005] We have discovered fuel compositions comprising synergistic
combinations of a biodiesel (B 100) or biodiesel blend (Bx), an antioxidant
comprising a mixture of at least one diphenol and at least one sterically
hindered
phenol, and a cetane improver. Notably, the fuel compositions described herein
evidence enhanced oxidation stability as determined by the Rancimat test
method (prEN 15751), even though they contain an ignition-enhancing,
oxidation stability-degrading cetane improver.
[006] In one aspect, the fuel compositions comprise: (1) between about
0.01% to about 1% by volume of a cetane improver; (2) either (a) a biodiesel,
or
(b) a biodiesel blend comprising about 2% to about 98% by volume of a
biodiesel and about 2% to about 98% by volume of a petroleum distillate; and
(3) an antioxidant comprising a mixture of at least one diphenol and at least
one
sterically hindered phenol, wherein (a) the amount of the antioxidant is (i)
between about 20 milligrams per kilogram of the biodiesel or biodiesel blend
to
about 10,000 milligrams per kilogram of the biodiesel or biodiesel blend, or
(ii)
is between about 16 milligrams per liter of the biodiesel or biodiesel blend
to
about 8,000 milligrams per liter of the biodiesel or biodiesel blend, and (b)
wherein the volumetric ratio of the diphenol(s) to the sterically hindered
phenol(s) is between about 0.01:1 to about 10:1.
[007] Given their unique combination of improved oxidation stability,
enhanced ignition quality and the fact that an antioxidant combination of a
sterically hindered phenol and diphenol is cheaper than a pure diphenol
antioxidant, the fuel compositions described herein facilitate a wider use of
biodiesels and biodiesel blends. Further, the fuel compositions described
herein

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should avoid the corrosion, plugging, and sediment and gum formation
associated with known biodiesels and biodiesel blends.
[0081 These and other aspects of the invention are described further in the
following detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0091 FIGURE 1 and FIGURE 2 illustrate that the addition of a cetane
improver to biodiesel fuels reduced their oxidation stability measured by the
Rancimat test method (prEN 15751), as determined in the experiment of
Example 1. As described in Examples 1-4 hereinafter, the fuels tested were
Fuel
1 (5% by volume of soybean methyl ester plus 95% by volume of petroleum
diesel fuel), Fuel 2 (99.7% by volume of Fuel 1 + 0.3% by volume of 2-
ethylhexyl nitrate), and variants of Fuel 2.
[010] FIGURE 3 illustrates the oxidation-stabilizing effect of adding a
diphenol and a sterically hindered phenol to biodiesel fuels containing a
cetane
improver, as determined in the experiment of Example 2.
[011] FIGURE 4 illustrates that the presence of a diphenol and a sterically
hindered phenol did not significantly affect the ignition quality of biodiesel
fuels
containing a cetane improver, as determined in the experiment of Example 3.
10121 FIGURE 5 illustrates that a benzoquinone proved ineffective as an
oxidation-stabilizing substitute for a diphenol, as determined in the
experiment
of Example 4.
DETAILED DESCRIPTION OF THE INVENTION
[0131 Unless otherwise stated, all percentages disclosed herein are on a
volume basis.
[014] Any end point of a range stated herein can be combined with any other
end point to form another suitable range.

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[0151 The following definitions apply unless indicated otherwise.
[016] "Biodiesel" means a composition that can be used as a fuel for diesel
engines and that contains at least about 50% by weight of esters of saturated
and
unsaturated fatty acids, including fatty acid methyl esters (FAME's), fatty
acid
ethyl esters (FAEE's), propyl esters of fatty acids, or combinations of two or
more methyl, ethyl, and propyl esters. In one example, a biodiesel comprises
between about 50% to about 99% by weight of methyl esters of saturated and
unsaturated fatty acids, where the methyl esters of saturated and unsaturated
fatty acids include C8-C24 fatty acid methyl esters, where C8-C24 indicates
the
number of carbons in the original fatty acid.
[0171 Biodiesels can be made by transesterification of one or more vegetable
oils, animal fats, or mixtures thereof (e.g. soybean oil, rapeseed oil, palm
oil,
canola oil, sunflower oil, olive oil, corn oil, tallow oil, coconut oil,
jatropha oil,
yellow grease, animal fats, used cooking oil, and mixtures thereof) with an
alcohol such as methanol or ethanol. In one aspect the fatty acid esters are
largely unsaturated and comprise a rapeseed methyl ester, a canola methyl
ester,
a soybean methyl ester, a corn oil methyl ester, or a mixture thereof. A 100%
biodiesel (B 100) should meet ASTM D6751 and/or EN 14214 specifications.
[0181 Biodiesel blends (biodiesel blended with a petroleum distillate such as
diesel fuel)(Bx) have a composition reflective of blend ratio and the
distillate
chosen for the blend.
10191 "Petroleum distillate" includes naphtha or middle distillates including
kerosene and diesel.
10201 A non-limiting example of a "diesel fuel" or "a diesel" is composed of
a mixture of C9-C24 hydrocarbons that comprise about 50% to about 95% by
volume of aliphatic hydrocarbons, of which about 0% to about 50% by volume
are eyeloparaffins, about 0% to about 5% by volume of olefinic hydrocarbons,

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and about 5% to about 50% by volume of aromatic hydrocarbons, and which
boil at between about 280 F (138 C) and 750 F (399 C).
[0211 A non-limiting example of a "kerosene" comprises about 5% to about
50% by volume of an aromatic fraction, about 0% to about 50% by volume of a
cycloparaffin fraction, and about 0% to about 5% by volume of an olefinic
fraction, with the rest comprising aliphatic hydrocarbons.
10221 An aromatics fraction can contain methyl aromatics and non-methyl
alkyl aromatics. Non-limiting examples of non-methyl alkyl aromatics include
molecules such as,alkyl benzenes, dialkylbenzenes, alkylnaphthalenes, alkyl
biphenyls, and alkyl phenanthrenes, and the like, in which one or more linear
or
branched alkyl groups containing two or more carbons is bonded to the aromatic
ring. Non-limiting examples of methyl aromatics include aromatic molecules
such as methylnaphthalene, dimethylnaphthalenes, and the like.
[0231 A cycloparaffin fraction consists of cycloalkanes or molecules
containing at least one cycloalkane ring. Non-limiting examples of components
of the cycloparaffin fraction include alkylcyclohexanes and
alkylcyclopentanes.
[0241 An olefinic fraction can contain linear, branched, and cyclo-olefins.
Non-limiting examples of components of the olefinic fraction include dodecenes
and hexadecenes.
[0251 A "cetane improver" includes but is not limited to 2-ethylhexyl nitrate
(EHN) (e.g. HITEC 4103, Ethyl Corp., Richmond, VA), cyclohexyl nitrate, di-
tert-butyl peroxide, methyl nitrate, ethyl nitrate, n-propyl nitrate,
isopropyl
nitrate, allyl nitrate, n-butyl nitrate, isobutyl nitrate, sec-butyl nitrate,
tert-butyl
nitrate, n-amyl nitrate, isoamyl nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-
amyl
nitrate, n-hexyl nitrate, 2-ethylhexyl nitrate, n-heptyl nitrate, sec-heptyl
nitrate,
n-octyl nitrate, sec-octyl nitrate, n-nonyl nitrate, n-decyl nitrate, n-
dodecyl
nitrate, cyclopenylnitrate, cyclohexylnitrate, methylcyclohexyl nitrate,

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isopropylcyclohexyl nitrate, and the esters of alkoxy substituted aliphatic
alcohols, such as 1-methoxypropyl-2-nitrate, 1-ethoxpropyl-2 nitrate, 1-
isopropoxy-butyl nitrate, 1-ethoxylbutyl nitrate, and mixtures thereof.
[026] A "diphenol" includes but is not limited to hydroquinone (HQ), mono
and dialkylated hydroquinones having one or two C1-C8 alkyl groups (e.g. tert-
butylhydroquinone (TBHQ), 2-tert-butyl- 1,4-hydroquinone, 2,5-di-tert-butyl-
1,4-hydroquinone, methylhydroquinone (toluhydroquinone or THQ), 2,5-di-tert.-
octylhydroquinone (DOH)), and mixtures thereof.
[027] A "sterically hindered phenol" includes but is not limited to mono, di,
and trialkylated phenols such as 2, 6-di-tert-butylphenol, 2, 4-di-tert-
butylphenol, 2, 6-di-tert-butyl-4-methylphenol (BHT), 2-tert-butylphenol, 2,
4,
6-tri-tert-butylphenol, 2, 6-di-tert-butyl-4-dimethylaminomethylphenol, and
mixtures thereof Commercially-available sterically hindered phenols that can
be used in the fuel compositions described herein include Ethanox 4703 and
4733 (Albermarle Corp., Baton Rouge, LA), Westco AO-29 (Western Reserve
Chemical, Stow, OH), Baynox (Lanxess, Leverkusen, DE), and Ionol BF
150 and BF 200 (Oxiris Chemicals S.A.., Barcelona, ES).
[028] In certain aspects, the diphenol and sterically hindered phenol are
selected, respectively, from a compound of formula (I) and a compound of
formula (II):
OH CH3 OH CH3
,C H3
/ C R3 C CH3
`CH3 I `CH3
R~ ~
OH R2
1 II
wherein R1 and R3 are H or a tert-butyl group and R2 is H, CH3, a tert-butyl
group or -CH2-N(CH3)2.

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[029] In one aspect, fuel compositions of the invention may also include an
aromatic amine antioxidant (e.g. a phenylediamine- type antioxidant) such as
N,
N'-di-sec-butyl-p-phenylenediamine, 4-isopropylaminodiphenylamine, phenyl-
naphthyl amine, and ring-alkylated diphenylamines.
[030] Fuel compositions of the invention may also include performance
additives such as cold flow additives, cloud point depressants, biocides,
conductivity improvers, corrosion inhibitors, metal deactivators, and engine
cleaning agents. In some aspects, such additives are present in an amount
which
ranges from about 0.001 to about 2.0% by weight of the fuel composition.
[031] In certain aspects, the fuel compositions comprise: (1) between about
0.01% to about 1%, in some aspects between about 0.01% to about 0.75%, in
some aspects between 0.0 1% to about 0.5%, and in some aspects between about
0.01% to about 0.35% by volume of a cetane improver; (2) either (a) a
biodiesel
comprising at least about 50% by weight, in some aspects at least about 60% by
weight, in some aspects at least about 70% by weight, in some aspects at least
about 80% by weight, in some aspects at least about 90% by weight, in some
aspects at least about 95% by weight of esters of saturated and unsaturated
fatty
acids, or (b) a biodiesel blend comprising about 2% to about 98% by volume of
a
biodiesel as described herein and about 2% to about 98% by volume of a
petroleum distillate, or in some aspects about 10% to about 90% by volume of a
biodiesel and about 10% to about 90% by volume of a petroleum distillate, or
in
some aspects about 20% to about 80% by volume of a biodiesel and about 20%
to about 80% by volume of a petroleum distillate, or in some aspects about 30%
to about 70% by volume of a biodiesel and about 30% to about 70% by volume
of a petroleum distillate, or in some aspects about 40% to about 60% by volume
of a biodiesel and about 40% to about 60% by volume of a petroleum distillate,
or in some aspects about 50% by volume of a biodiesel and about 50% by
volume of a petroleum distillate, or in some aspects about 30% by volume of a
biodiesel and about 70% by volume of a petroleum distillate, or in some
aspects

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about 20% by volume of a biodiesel and about 80% by volume of a petroleum
distillate, or in some aspects about 5-10% by volume of a biodiesel and about
90-95% by volume of a petroleum distillate; and (3) an antioxidant comprising
a
mixture of at least one diphenol and at least one sterically hindered phenol,
wherein (a) the amount of the antioxidant is (i) between about 20 milligrams
per
kilogram of the biodiesel or biodiesel blend to about 10,000 milligrams per
kilogram of the biodiesel or biodiesel blend, or in some aspects is between
about
100 milligrams per kilogram of the biodiesel or biodiesel blend to about 5,000
milligrams per kilogram of the biodiesel or biodiesel blend, or in some
aspects is
between about 100 milligrams per kilogram of the biodiesel or biodiesel blend
to
about 1,000 milligrams per kilogram of the biodiesel or biodiesel blend, or in
some aspects is between about 100 milligrams per kilogram of the biodiesel or
biodiesel blend to about 500 milligrams per kilogram of the biodiesel or
biodiesel blend, or (ii) in some aspects is between about 16 milligrams per
liter
of the biodiesel or biodiesel blend to about 8,000 milligrams per liter of the
biodiesel or biodiesel blend, or in some aspects is between about 100 or about
200 milligrams per liter of the biodiesel or biodiesel blend to about 400 or
about
500 milligrams per liter of the biodiesel or biodiesel blend, and wherein (b)
the
volumetric ratio of the diphenol(s) to the sterically hindered phenol(s) is
between
about 0.01:1 to about 10:1, or in some aspects is about 0.1:1, or in some
aspects
is about 0.25:1, or in some aspects is about 0.5:1, or in some aspects is
about
0.75:1, or in some aspects is about 0.9:1, or in some aspects is about 1:1, or
in
some aspects is about 1.25:1, or in some aspects is about 1.5:1.
[032] In some aspects, the fuel compositions comprise: (1) between about
0.1% to about 0.35% by volume of a cetane improver; (2) a biodiesel blend
comprising (a) about 5% to about 30% by volume of a biodiesel comprising a
fatty acid ester selected from the group consisting of rapeseed methyl ester,
a
canola methyl ester, a soybean methyl ester, a corn oil methyl ester, or a
mixture
thereof, and (b) about 70 to about 95% by volume of a diesel; and (3) an

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antioxidant comprising (a) a diphenol selected from the group consisting of
tert-
butylhydroquinone, 2-tert-butyl- 1,4-hydroquinone, 2,5-di-tert-butyl- 1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and (b)
a sterically hindered phenol selected from the group consisting of 2, 6-di-
tert-
butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-butyl-4-methylphenol, 2-
tert-
butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-tert-butyl-4-
dimethylaminomethylphenol, wherein (a) the amount of the antioxidant is
between about 100 milligrams per liter biodiesel blend to about 500 milligrams
per liter of the biodiesel blend, and wherein (b) the volumetric ratio of the
diphenol to the sterically hindered phenol is between about 0.5:1 to about
1.5:1.
[033] In some aspects, the fuel compositions comprise: (1) between about
0.1% to about 0.35% by volume of a cetane improver; (2) a biodiesel blend
comprising (a) about 5% to about 15% by volume of a biodiesel comprising a
fatty acid ester selected from the group consisting of rapeseed methyl ester,
a
canola methyl ester, a soybean methyl ester, a corn oil methyl ester, or a
mixture
thereof, and (b) about 85 to about 95% by volume of a diesel; and (3) an
antioxidant comprising (a) a diphenol selected from the group consisting of
tert-
butylhydroquinone, 2-tert-butyl-1,4-hydroquinone, 2,5-di-tert-butyl-1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and (b)
a sterically hindered phenol selected from the group consisting of 2, 6-di-
tert-
butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-butyl-4-methylphenol, 2-
tert-
butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-tert-butyl-4-
dimethylaminomethylphenol, wherein (a) the amount of the antioxidant is
between about 200 milligrams per liter of the biodiesel blend to about 400
milligrams per liter of the biodiesel blend, and wherein (b) the volumetric
ratio
of the diphenol to the sterically hindered phenol is between about 0.75:1 to
about
1:1.
[0341 In some aspects, the fuel compositions comprise: (1) between about
0.1% to about 0.35% by volume of a cetane improver; (2) a biodiesel blend

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comprising (a) about 5% to about 15% by volume of a biodiesel comprising
between about 50% to about 99% by weight of methyl, ethyl, and propyl esters
of saturated and unsaturated fatty acids, and (b) about 85 to about 95% by
volume of a diesel; and (3) an antioxidant comprising (a) a diphenol selected
from the group consisting of tert-butylhydroquinone, 2-tert-butyl-1,4-
hydroquinone, 2,5-di-tert-butyl-1,4-hydroquinone, methylhydroquinone, and
2,5-di-tert.-octylhydroquinone, and (b) a sterically hindered phenol selected
from the group consisting of 2, 6-di-tert-butylphenol, 2, 4-di-tert-
butylphenol, 2,
6-di-tert-butyl-4-methylphenol, 2-tert-butylphenol, 2, 4, 6-tri-tert-
butylphenol,
and 2, 6-di-tert-butyl-4-dimethylaminomethylphenol, wherein (a) the amount of
the antioxidant is between about 200 milligrams per liter of the biodiesel
blend
to about 400 milligrams per liter of the biodiesel blend, and wherein (b) the
volumetric ratio of the diphenol to the sterically hindered phenol is between
about 0.75:1 to about 1:1.
[035] In some aspects, the fuel compositions comprise: (1) between about
0.1% to about 0.35% by volume of 2-ethylhexyl nitrate; (2) a biodiesel blend
comprising (a) about 5% to about 10% by volume of a biodiesel comprising a
fatty acid ester selected from the group consisting of rapeseed methyl ester,
a
canola methyl ester, a soybean methyl ester, a corn oil methyl ester, or a
mixture
thereof, and (b) about 90% to about 95% by volume of a diesel; and (3) an
antioxidant comprising (a) a diphenol selected from the group consisting of
tert-
butylhydroquinone, 2-tert-butyl- 1,4-hydro qui none, 2, 5 -di-tert-butyl-1,4-
hydroquinone, methylhydroquinone, and 2,5-di-tert.-octylhydroquinone, and (b)
a sterically hindered phenol selected from the group consisting of 2, 6-di-
tert-
butylphenol, 2, 4-di-tert-butylphenol, 2, 6-di-tert-butyl-4-methylphenol, 2-
tert-
butylphenol, 2, 4, 6-tri-tert-butylphenol, and 2, 6-di-tert-butyl-4-
dimethylaminomethylphenol, wherein (a) the amount of the antioxidant is
between about 200 milligrams per liter of the biodiesel blend to about 400
milligrams per liter of the biodiesel blend, and wherein (b) the volumetric
ratio

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of the diphenol to the sterically hindered phenol is between about 0.9:1 to
about
1:1.
[036] In some aspects, the fuel compositions comprise: (1) between about
0.1% to about 0.35% by volume of 2-ethylhexyl nitrate; (2) a biodiesel blend
comprising (a) about 5% to about 10% by volume of a biodiesel comprising a
fatty acid ester selected from the group consisting of rapeseed methyl ester,
a
canola methyl ester, a soybean methyl ester, a corn oil methyl ester, or a
mixture
thereof, and (b) about 90% to about 95% by volume of a diesel; and (3) a
diphenol and a sterically hindered phenol selected, respectively, from a
compound of formula (I) and a compound of formula (II):
OH C 3 OH CH3
3 / C CH3
C.
CH3 R3 I `CH3
R ~
OH R2
I II
wherein:
(a) Ri and R3 are H or a tert-butyl group, and R2 is H, CH3, a tert-butyl
group or -
CH2-N(CH3)2; (b) the amount of the antioxidant is between about 100 milligrams
per liter biodiesel blend to about 500 milligrams per liter of the biodiesel
blend,
and wherein (c) the volumetric ratio of the diphenol to the sterically
hindered
phenol is between about 0.5.1 to about 1.5:1.
[037] In some aspects, the fuel compositions comprise: (1) between about
0.1% to about 0.35% by volume of 2-ethylhexyl nitrate; (2) a biodiesel
comprising about a fatty acid ester selected from the group consisting of
rapeseed methyl ester, a canola methyl ester, a soybean methyl ester, a corn
oil
methyl ester, or a mixture thereof; and (3) a diphenol and a sterically
hindered
phenol selected, respectively, from a compound of formula (1) and a compound
of formula (II):

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OH C H3 OH CH3
C. a / C CH3
CH3 R3 I CH3
R~ ~
OH R2
! I!
wherein
(a) Rl and R3 are H or a tert-butyl group, and R2 is H, CH3, a tert-butyl
group or -
CH2-N(CH3)2; (b) the amount of the antioxidant is between about 200 milligrams
per liter of the biodiesel blend to about 400 milligrams per liter of the
biodiesel
blend, and wherein (c) the volumetric ratio of the diphenol to the sterically
hindered phenol is between about 0.9:1 to about 1:1.
10381 These and other aspects of the fuel compositions described herein are
illustrated further in the following examples, which are illustrative and are
not
limiting.
Experimental Apparatus and Methods
[0391 The following experimental apparatus and methods were used in the
experiments of Examples 1-4 described below.
[0401 Experiments were undertaken in accord with the Rancimat test method
(prEN 15751). The Rancimat test is carried out by passing a steady stream of
air
through a heated (110 C) sample and measuring the volatile oxidation species
produced over a period of time. The point at which the rate of production of
the
volatile oxidation species reaches a maximum is defined as the induction
period
or oxidation stability (measured in hours at the given temperature) and
provides
a characteristic value for oxidation stability.
[041] Specifically, oxidation is induced by passing a stream of purified air
at
the rate of 10 liters/hr through the biodiesel sample (approx. 7.5 g), kept at
constant temperature. The vapors released during the oxidation process,
together
with the air, are passed into the flask containing 60 ml of water which has
been

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demineralized or distilled and contains an electrode for measuring the
conductivity. The electrode is connected to a measuring and recording device.
The end of the induction period is indicated when the conductivity begins to
increase rapidly. This accelerated increase in conductivity is caused by the
dissociation of volatile carboxylic acids which are produced during the
oxidation
process and which are absorbed in the water. When the conductivity of this
measuring solution is recorded continuously, an oxidation curve is obtained
whose point of inflection indicates the induction period; which provides the
characteristic value for the oxidation stability. The EN 14214 Standard for
the
B 100 and ASTM D7467 Standard for the B6-B20 biodiesel fuels specify a
Rancimat induction period of six hours minimum.
Example 1
[042] We unexpectedly found that the presence of a cetane improver such as
2-ethylhexyl nitrate improves the ignition quality of, and degrades the
Rancimat
oxidation stability of, a biodiesel blend or a biodiesel. Sterically hindered
phenolic antioxidants improved the oxidation stability of the biodiesel or
biodiesel blend fuels, but not to the same extent as a diphenol such as tert-
butylhydroquinone antioxidant. However, a combination of a sterically hindered
phenolic antioxidant with a diphenol such as tert-butylhydroquinone provided
similar, and in some cases even directionally better, oxidation stability when
compared to the use of only a diphenol.
[043] The experiment of this example shows that the addition of a 2-
ethylhexyl nitrate cetane improver to a biodiesel fuel reduced its Rancimat
(prEN 15751) oxidation stability by about 26.5% (average of 2 Rancimat
stability results). As listed below and as depicted in Figures 1 and 2, upon
addition of the cetane improver, oxidation stability decreased for each of the
fuels tested.

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Figure 1
Fuel 1: 5 vol% Soybean Methyl Ester + 95 vol% petroleum diesel fuel
Fuel 2: 99.7 vol% Fuel 1 + 0.3 vol% 2-ethylhexyl nitrate
Comparative Examples (Figure 2)
B5 SME (no EHN) 28.4 hours
B5 SME + 0.1 vol% EHN 23.7 hours (16.6% Rancimat stability redution)
B5 SME + 0.2 vol% EHN 20.4 hours (28.2% Rancimat stability reduction)
B5 SME + 0.35 vol% EHN 10.3 hours (63.7% Rancimat stability reduction)
Example 2
[044] The experiment of this example shows that sterically hindered
phenolic antioxidants improve the Rancimat stability of biodiesel fuel
containing
a cetane improver, but not to the same extent as a diphenol such as 2-tert-
buty1hydroquinone. However, as seen in Figure 3, a mixture of a 50% by volume
2-tert-butylhydroquinone with 50% by volume of sterically hindered phenols
provided significantly better Rancimat stability than the calculated Rancimat
stability for that composition.
Figure 3
Fuel 3: Fuel 2 + 400 mg/L Ethanox 4733
Fuel 4: Fuel 2 + 400 mg/L Ethanox 4703
Fuel 5: Fuel 2 + 400 mg/L 2-tert-butyl- 1,4-hydroquinone
Fuel 6: Fuel 2 + 200 mg/L Ethanox 4703 + 200mg/L 2-tert-butyl-1, 4-
hydroquinone
Fuel 7: Fuel 2 + 200 mg/L Ethanox 4733 + 200 mg/L 2-tert-butyl-1, 4-
hydroquinone
Fuel 8: Fuel 6 calculated Rancimat stability
Fuel 9: Fuel? calculated Rancimat stability

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Example 3
[0451 The experiment of this example shows (as depicted in Figure 4) that
the 2-ethylhexyl nitrate cetane improver increases the ASTM D6890 ignition
quality of the biodiesel Fuels 1-7 and that the presence of antioxidants did
not
significantly affect the ignition quality of the biodiesel fuels. Fuels 1-7
were
comprised of Fuels 1 or 2 (Example 1).
Fiugre4
Fuel 1: 5 vol% Soybean Methyl Ester + 95 vol% petroleum diesel fuel
Fuel 2: 99.7 vol% Fuel 1 + 0.3 vol% 2-ethylhexyl nitrate
Fuel 3: Fuel 2 + 400 mg/L Ethanox 4733
Fuel 4: Fuel 2 + 400 mg/L Ethanox 4703
Fuel 5: Fuel 2 + 400 mg/L 2-tert-butyl-1,4-hydroquinone
Fuel 6: Fuel 2 + 200 mg/L Ethanox 4703 + 200mg/L 2-tert-butyl-1, 4-
hydroquinone
Fuel 7: Fuel 2 + 200 mg/L Ethanox 4733 + 200 mg/L 2-tert-butyl-1, 4-
hydroquinone
Example 4
10461 The experiment of this example shows (as depicted in Figure 5) that
compared to a diphenol such as tert-butylhydroquinone, a benzoquinone such as
2,6-di-tert-butyl [1, 4] benzoquinone (formula (111)) proves ineffective as an
antioxidant..
H3C` O CH3
H3CC C ,CH3
H3 / I I `CH3
0
III
Figure 5
Fuel 2: 99.7 vo1% Fuel 1 + 0.3 vol% 2-ethythexyl nitrate

CA 02767928 2012-01-11
WO 2011/014424 PCT/US2010/043039
- 16-
Fuel 3: Fuel 2 + 400 mg/L Ethanox 4733
Fuel 4: Fuel 2 + 400 mg/L Ethanox 4703
Fuel 10: Fuel 2 + 400 mg/L 2,6-di-tert-butylbenzoquinone
Fuel 11: Fuel 2 + 200 mg/L Ethanox 4733 + 200 mg/L 2,6-di-tert-
butylbenzoquinone
Fuel 12: Fuel 2 + 200 mg/L Ethanox 4703 + 200 mg/L 2,6-di-tert-
butylbenzoquinone
Fuels 2, 3, 4, 10, 11, and 12 were comprised of Fuels 1 or 2 (Example 1).
1047] It is to be understood that the above description is intended for
illustrative purposes only and is not intended to limit the scope of the
present
invention in any way.

Dessin représentatif