U.S. patent application number 10/126658 was filed with the patent office on 2002-12-05 for low temperature stable diesel oil/alcohol mixtures.
Invention is credited to Hogan, Edward, Ikura, Michio, Stanciulescu, Maria.
Application Number | 20020178650 10/126658 |
Document ID | / |
Family ID | 23105769 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020178650 |
Kind Code |
A1 |
Ikura, Michio ; et
al. |
December 5, 2002 |
Low temperature stable diesel oil/alcohol mixtures
Abstract
A low temperature stable diesel fuel composition includes diesel
oil, ethanol, and a solubliser of C.sub.14-C.sub.18 fatty acids
from biodegradable sources e.g. tall oil or depitched tall oil.
This fuel remains stable at temperatures as low as -20.degree.
C.
Inventors: |
Ikura, Michio; (Kanata,
CA) ; Stanciulescu, Maria; (Orleans, CA) ;
Hogan, Edward; (Ottawa, CA) |
Correspondence
Address: |
Norris M. Eades
KIRBY EADES GALE BAKER
P.O. Box 3432, Station D
Ottawa, Ontario
K1P 6N9
CA
|
Family ID: |
23105769 |
Appl. No.: |
10/126658 |
Filed: |
April 22, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60288109 |
May 3, 2001 |
|
|
|
Current U.S.
Class: |
44/438 |
Current CPC
Class: |
C10L 1/026 20130101;
Y02E 50/10 20130101; Y02E 50/13 20130101; C10L 1/1888 20130101 |
Class at
Publication: |
44/438 |
International
Class: |
C10L 001/18 |
Claims
1. A low temperature stable diesel fuel composition which
comprises: (a) diesel oil; (b) ethanol; and (c) a solubliser
comprising fatty acids derived from biodegradable sources having
chain lengths of C.sub.14-18.
2. A low temperature stable diesel fuel composition according to
claim 1, wherein the fuel remains stable at temperatures lower than
0.degree. C.
3. A low temperature stable fuel composition according to claim 1,
wherein the ethanol and diesel oil are present in the proportion of
from about 5% to about 85% by weight ethanol and from about 15% to
about 95% by weight diesel oil.
4. A low temperature stable diesel fuel composition according to
claim 3, wherein the solubliser is present in an amount of up to
20% by weight based on the total fuel composition.
5. A low temperature stable diesel fuel composition according to
claim 1, wherein the ethanol is substantially anhydrous.
6. A low temperature stable diesel fuel composition according to
claim 5, wherein the ethanol comprises about 5% to 20% by weight of
the composition.
7. A low temperature stable diesel fuel composition according to
claim 1, wherein the solubliser comprises fatty acids derived from
tall oil.
8. A low temperature stable diesel fuel composition according to
claim 7, wherein the solubliser comprises depitched tall oil.
9. A low temperature stable diesel fuel composition according to
claim 1, with a cetane number of more than 40.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Provisional
Application 60/288,109, filed May 3, 2001.
BACKGROUND OF THE INVENTION
[0002] This invention relates to low temperature stable diesel
oil/ethanol mixtures and, more particularly, to biodegradable
solubliser additives that promote the low temperature
stability.
[0003] The hope afforded to nuclear fusion and hydrogen fuel cell
technology is likely to be years, or perhaps decades, from
commercial viability. In the meantime, demand for oil continues to
rise, resulting in increasing pressure to find alternative energy
resources. In particular, the world's finite reserves of oil
represent a non-renewable source of energy. For this reason, it is
imperative to find ways to reduce the consumption of traditional
petroleum-based oil, and increase the use of alternative, renewable
fuels.
[0004] The powering of diesel engines accounts for a significant
proportion of oil consumption worldwide. A typical diesel oil is a
petroleum gas oil (middle distillate), with additives present in
very small amounts relative to the diesel oil. These additives
improve the combustion efficiency of the diesel oil, resulting in
increased engine efficiency and performance, as well as reduced
particulate emissions. For example, U.S. Pat. No. 4,451,266 teaches
a corresponding additive that can be mixed with diesel oil in a
1:500 to 1:2000 ratio, the additive comprising 3-10% methanol or
ethanol, 3-13% halogenated alkene, 3-13% aromatic hydrocarbon,
35-70% of naptha range hydrocarbon, and 20-30% of
hydroxy-substituted unsaturated fatty acids.
[0005] To date, research in this field has investigated the
production of alternative fuel blends with reduced diesel oil
content, capable of powering a diesel engine. In some cases, fuels
have been developed which lack diesel oil as a constituent. For
example, U.S. Pat. No. 4,929,252 discloses an castor oil/ethanol
blend that may be used to power a diesel engine. In another
example, U.S. Pat. No. 4,937,655 discloses a vegetable oil/ethanol
mixture for use as a diesel engine fuel, wherein the addition of a
ketal, acetal or orthoester to the mixture converts any trace of
contaminating water to alcohol, thus discouraging phase separation
of the oil/ethanol mix. Whilst these "bio-oil" fuels represent
interesting alternatives to hydrocarbon-containing fuels, they
inevitably contain a high proportion of glycerides. In this regard,
it is well understood in the art that use of these fuels can often
give rise to glyceride pyrolysis, which unavoidably results in
engine gumming. The resulting buildup of deposits within the engine
can result in poor engine performance and efficiency. In addition,
the high viscosity of "bio-oil" fuels can affect their
compatibility for direct use in a diesel engine. In some cases,
diesel engines must be significantly modified to accommodate the
specific characteristics of these alternative fuels.
[0006] In the light of the problems encountered with "bio-oil"
fuels, more recent innovations in diesel engine fuel technology
have focussed upon fuel blends that include a proportion of diesel
oil. In particular, it is well known in the art that ethanol can be
used in diesel oil blends to produce a fuel suitable for use in a
diesel engine. Ethanol confers several advantages over alternative
constituents. Ethanol can be easily produced on an industrial
scale, and thus represents a readily renewable source of energy. As
an oxygenate, it could enhance combustion characteristics.
[0007] The key difficulty in providing a diesel oil/ethanol fuel
blend, suitable for use in a diesel engine, arises from the limited
miscibility of the two components. Although small amounts of
ethanol and diesel oil are miscible at room temperature, slight
contamination with water separates the mixture into two phases. In
addition, the miscibility of diesel oil and ethanol is reduced at
lower temperatures. One way of mixing diesel oil and ethanol
involves the production of micro-emulsions. For example, U.S. Pat.
No. 4,477,258 discloses a diesel fuel emulsion comprising diesel
oil and an aqueous solution of ethanol or methanol together with an
emulsifying blend of sorbitan monooleate and a water soluble
ethoxylated non-ionic surfactant. In another example, U.S. Pat. No.
4,451,265 discloses a hybrid diesel fuel composition in which water
and alcohol are held in a stable microemulsion by means of a
surfactant system comprising N,N-dimethylethanolamine and a long
chain fatty acid.
[0008] It must be mentioned that, to maintain a thermodynamically
stable emulsion, the size of the alcohol droplets must be very
small. This in turn requires a large quantity of surfactant in the
fuel blend. In this regard, surfactant is a relatively expensive
constituent, and the cost of the resulting fuel can be unacceptably
high. Microemulsions have a further disadvantage with regard to
production costs. The production of stable microemulsions requires
intensive mixing/stirring high volumes of fuel on an industrial
scale that escalates the production cost even higher. Further, when
a diesel fuel tank is filled with the emulsion fuel, one must
remain with the particular emulsion fuel, and cannot be switched to
regular diesel fuel. This is because when emulsion fuel is diluted
by regular diesel, the stability of emulsion fuel deteriorates
resulting in phase separation.
[0009] As an alternative to microemulsions, it is also possible to
mix diesel oil and alcohol together as a solution, which relies
upon the miscibility of the two components. Diesel oil and
anhydrous ethanol are readily miscible at room temperature.
However, it is well known in the art that lower temperatures, or a
small amount of contaminating water, result in the separation of
the diesel oil and ethanol into distinct phases. A fuel that is
easily prone to phase separation is unsuitable for use in a diesel
engine. For this reason, it is highly desirable to produce diesel
oil/ethanol fuel blends in which the diesel oil and ethanol form a
homogeneous and stable solution.
[0010] In one attempt to achieve this objective, U.S. Pat. No.
4,405,337 discloses a diesel oil/alcohol fuel blend comprising a
solubliser in the form of castor oil. In this example, the castor
oil is shown to induce the miscibility of the diesel oil and an
aqueous solution of alcohol, wherein the alcohol component
comprises 0.5% water. At 25.degree. C. the castor oil induces
solublisation of the diesel oil and alcohol at most relative
concentrations of the constituents. However, at 10.degree. C. and
at 0.degree. C. the solublisation characteristics are limited. Fuel
mixtures comprising less than 20% castor oil, and more than 20%
ethanol, will generally separate into two phases at 0.degree. C.
U.S. Pat. No. 4,405,337 does not disclose the use of castor oil
fuel blends at temperatures below 0.degree. C.
[0011] In another example, U.S. Pat. No. 6,017,369 discloses fuel
compositions comprising diesel oil, ethanol, an alkyl ester of a
fatty acid, and a stabilizer (of specific ether or ether/amide
mixtures). Fuel blends comprising diesel oil/ethanol solutions are
described that are stable at temperatures as low as -19.degree. C.
Such fuel blends comprise a complex mixture of additives to achieve
reasonable levels of low temperature stability.
[0012] In the developed world, vehicles that are powered by diesel
engines comprise the majority of smaller vans and trucks, and
nearly all large trucks, buses and non-electrically powered trains.
In Europe, diesel oil powered cars comprise an increasingly
significant market share. This has resulted from a new generation
of direct-injection engines, which are more refined and powerful
than their predecessors. The modern diesel engine is considerably
more efficient than the equivalent gasoline engine, so further
improvements to generate "greener" diesel engines, which use even
less hydrocarbon-based fuel, could play a key role in the reduction
of petroleum consumption and the protection of the environment.
However, the development of alternative "hybrid" diesel engine
fuels has so far been restricted by the limitation of temperature
stability. Much of the developed world exists in regions of cold
climates with temperatures frequently falling below 0.degree. C.
Other regions with less cold climates nevertheless experience cold
conditions during the winter months. Therefore, to be commercially
viable, any new fuel for a diesel engine must have the property of
low temperature stability.
[0013] It is an object of the present invention to provide improved
low temperature stable diesel fuels, in the form of homogeneous
liquid mixtures of diesel oil and alcohol, comprising a
biodegradable oxygenate as a solubliser. Furthermore, it is an
object the present invention to provide a solubliser that may be
used in low concentrations to successfully achieve homogeneity of
diesel oil/alcohol mixtures at low temperatures, without the risk
of glyceride pyrolysis. It is a further object of the present
invention to provide fuel blends that exhibit superior levels of
stability at temperatures of less than 0.degree. C., preferably
less than -5.degree. C.
SUMMARY OF INVENTION
[0014] The present invention provides low temperature stable diesel
fuel compositions which comprise diesel oil, ethanol, and a
solubliser comprising fatty acids having chain lengths of
C.sub.14-18. The inclusion of specific fatty acids in diesel
oil/ethanol fuel blends can induce the formation of stable
homogeneous solutions at temperatures considerably lower than
0.degree. C., e.g. below -20.degree. C. In the fuel composition of
the present invention, it is important to note that the components
are dissolved in one another and the fuel is free of emulsions. The
ethanol and diesel oil are typically present in the proportion of
5:95 to 85:15 by weight. The solubliser is typically added to the
diesel oil/ethanol mixture in an amount up to 20% by weight based
on the total fuel composition. The solubliser can be a fatty acid
derived from a variety of biodegradable sources. Particularly
useful solublisers include tall oil and depitched tall oil (tall
oil from which heavy bottoms material has been removed). Depitched
tall oil is free of glycerides and thus very suitable as a diesel
fuel component. Importantly, tall oil has been unexpectedly found
to provide for significantly improved temperature stability of
diesel oil/ethanol solutions, thus permitting larger proportions of
ethanol to remain dissolved in diesel oil at lower ambient
temperatures. The fuels of the present invention may be widely used
to power diesel engines under conditions where low ambient
temperature is an important consideration.
DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a graph to show the phase separation
characteristics of diesel oil/ethanol mixtures over a range of
depitched tall oil concentrations;
[0016] FIG. 2 is a graph to compare the volume of the separate
(ethanol) phase of azeotropic ethanol/diesel oil mixtures in the
presence or absence of depitched tall oil (wherein D=diesel oil,
ZE=azeotropic ethanol, and DPTO=depitched tall oil);.
[0017] FIG. 3 is a graph to compare the capacity of depitched tall
oil, canola methyl esters and corn methyl esters, to solublise
diesel oil and ethanol (wherein D=diesel oil, ZE=azeotropic
ethanol, CAME=canola methyl esters, and COME=corn methyl esters);
and
[0018] FIG. 4 is a graph to analyze the capacity of canola methyl
esters to solublise diesel oil/ethanol mixtures over a range of
temperatures (wherein E=anhydrous ethanol, D=diesel oil, and
CAME=canola methyl esters).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] Examples are provided with particular reference to depitched
tall oil as a solubliser. Tall oil is a by-product of the pulping
of resinous softwoods such as spruce and pine. Pulp spent liquor is
treated with sulfuric acid before being collected as crude tall
oil. In this way, the sufuric acid reacts with glycerides present
in the liquor. Crude tall oil comprises fatty acids in the C.sub.16
to C.sub.24 range, but the principle components are unsaturated
C.sub.18 fatty acids, diterpenic rosin acids and unsaponifiable
neutrals such as sterols. Crude tall oil also contains a small
amount of sugars. However, when crude tall oil is depitched the
rosin acids, neutrals and sugars remain in the heavy ends, an thus
depitched tall oil comprises primarily C.sub.16 to C.sub.18 fatty
acids. The composition of depitched tall oil therefore provides
significant advantages over diesel oil/ethanol solublisers of the
prior art, since prior treatment with sulfuric acid renders the oil
substantially free of gycerides, thus resulting in reduced
glyceride pyrolysis during combustion.
EXAMPLE 1
[0020] A series of tests were conducted on different mixtures of
anhydrous ethanol, #2 diesel oil, and a solubliser as shown in
Table 1 below:
1 TABLE 1 Cetane Flash Diesel oil ethanol mixtures with number
point a solubliser Certified #2 diesel oil only 45.7 86 5wt %
ethanol + 94wt % #2 diesel + 43.1 16 1wt % depitched tall oil 5wt %
ethanol + 94wt % #2 diesel + 43.3 1wt % esterified canola oil 5wt %
ethanol + 94wt % #2 diesel + 43.2 1wt % esterified corn oil 5wt %
ethanol + 94wt % #2 diesel + 43.6 1wt % esterified soy oil 10wt %
ethanol + 88wt % #2 diesel + 39.5 15 2wt % depitched tall oil 20wt
% ethanol + 76wt % #2 diesel + 33.2 15 4wt % depitched tall oil
[0021] The cetane numbers and flash points were determined as shown
above. In consideration of Table 1, the cetane numbers remain high
for fuel mixtures comprising only 5% ethanol. However, at higher
ethanol concentrations the cetane numbers are lower. Therefore, the
diesel fuel mixtures of the present invention, which comprise
higher concentrations of ethanol, may require additional spiking to
ensure suitable combustion characteristics. From Table 1, it will
be noted that fuels comprising more than 5% ethanol have lower
flash points. It is expected that combustion of such fuel mixtures
will result in lower NO.sub.x emissions as a result of the lower
combustion temperatures. Moreover, the ethanol, a simple oxygenate,
in the mixtures will also result in reduced particulate emissions.
Therefore, the fuel mixtures may present significant advantages in
terms of reduced environmental pollutants.
EXAMPLE 2
[0022] The fuel mixtures containing depitched tall oil were tested
for temperature stability. This was done by measuring the
temperature at which phase separation takes place. As the
solubliser, fatty acids in the form of depitched tall oil have been
found to be particularly effective. The graph shown in FIG. 1
displays the boundaries of phase separation for anhydrous ethanol
and diesel oil at different temperatures and tall oil
concentrations. FIG. 1 demonstrates that tall oil considerably
enhances the capacity of ethanol and diesel oil to form a
solution.
[0023] Two general considerations can be made regarding FIG. 1.
Firstly, the graph shows that diesel oil/ethanol mixtures,
comprising roughly equal quantities (by weight) of each component,
require the highest amount of tall oil additive to ensure that a
homogeneous solution is maintained. This point is relevant
regardless of the temperature. In mixtures comprising unequal
amounts of diesel oil and ethanol, a smaller amount of tall oil may
be added to achieve homogeneity. The second consideration relates
to temperature. FIG. 1 demonstrates that at lower temperatures,
more tall oil is required to achieve homogeneity of a particular
diesel oil/ethanol mixture.
[0024] In general, higher amounts of tall oil are needed to ensure
complete solublisation of diesel oil and ethanol at lower
temperatures. In the prior art, similar observations have been made
with alternative solublisers. However, it is important to note that
solublisers of the prior art are required in unsatisfactorily high
concentrations to achieve solublisation at low temperatures. This
is known in the art to potentially give rise to engine gumming and
poor engine efficiency. In contrast, the present invention
discloses a fuel that is stable at low temperatures, wherein the
solubliser can generally be used in concentrations that are
considerably lower than those of the prior art. Accordingly, the
fuel compositions of the present invention are expected to be less
prone to engine gumming and poor engine efficiency.
[0025] According to FIG. 1, at -15.degree. C. the highest amount of
tall oil needed is only about 9% of the total volume by weight.
With mixtures comprising unequal amounts of diesel oil and ethanol,
the amount of tall oil required is even lower. The unexpected
superior solublisation properties of tall oil and other similar
oils over the solublisers of the prior art represent a significant
development in the formulation of "greener" diesel engine fuels,
which comprise lower amounts of non-replaceable hydrocarbon-based
oil products.
[0026] From FIG. 1 it is also apparent that for a particular diesel
oil/ethanol mixture, the amount of tall oil required increases
linearly as the temperature decreases. Based on these results, it
is expected that diesel oil/ethanol mixtures can be obtained that
are stable at temperatures of -40.degree. C. or lower with the
addition of less than 20% tall oil. Depitched tall oil is free of
sugar and glycerides. Therefore, the fuels of the present invention
have the potential to be used successfully in diesel engines at
ambient temperatures that are considerably lower than 0.degree.
C.
EXAMPLE 3
Depitched Tall Oil Descreases Phase Separation of Diesel
Oil/Azeotropic Ethanol Solutions
[0027] Water contamination of diesel oil/ethanol solutions can
result in phase separation of the diesel oil and ethanol. It is
known in the art that azeotropic ethanol (ethanol containing 4%
water) does not readily form a solution with diesel oil.
Experiments were performed to determine the ability of depitched
tall oil to increase the solubility of diesel oil and azeotropic
ethanol. Diesel oil/azeotropic ethanol mixtures comprising 10%, 20%
and 30% azeotropic ethanol were analyzed at temperatures ranging
from -15.degree. C. to 20.degree. C. (FIG. 2). The graph
demonstrates that separation of the mixtures into 2 distinct phases
occurred at all azeotropic ethanol concentrations, regardless of
the presence of depitched tall oil. However, for azeotropic ethanol
concentrations of 10% or 20%, the presence of depitched tall oil in
the mixtures significantly reduced the volume of the separated
(ethanol) phase for all temperatures tested. The depitched tall oil
therefore induced the ability of the azeotropic ethanol to
homogeneously dissolve in the diesel oil.
EXAMPLE 4
Comparison of Depitched Tall Oil with Methyl Esters of Canola and
Corn
[0028] Further experimentation was carried out using a diesel fuel
mixture comprising 5% azeotropic ethanol (FIG. 3), to compare the
solublisation capacities of depitched tall oil with canola methyl
esters and corn methyl esters. In the absence of additive, the
mixture remained in two phases at all temperatures tested
(-15.degree. C. to 20.degree. C.; FIG. 3). However, when a small
amount of depitched tall oil was added to the mixture, the
homogeneity was achieved at temperatures ranging from 10.degree. C.
to 20.degree. C., although a very small second phase appeared at
temperatures lower than 5.degree. C. (FIG. 3). These results
suggest that the fuel mixtures of the present invention should
preferably comprise less than 0.2% moisture.
[0029] The solublisation characteristics of depitched tall oil were
compared with those of canola methyl esters and corn methyl esters.
Unexpectedly, the canola and corn methyl esters decreased the
ability of the mixture to form a homogeneous solution at all
temperatures tested, resulting in an increase in the volume of the
separated (ethanol) phase. This was in complete contrast to the
depitched tall oil, which increased the homogeneity of the mixture
significantly. In conclusion, when moisture is present, the
depitched tall oil exhibits properties that induce the formation of
diesel oil/ethanol solutions, unlike the selected methyl esters
tested.
EXAMPLE 5
Depitched Tall Oil is a Significantly more Efficient Solubliser
than Canola Methyl Esters for Diesel Oil/Anhydrous Ethanol
Mixtures
[0030] Experiments were carried out to analyze the ability of
canola methyl esters to solublise mixtures of diesel oil and
anhydrous ethanol (FIG. 4). The presence of canola methyl esters
can maintain homogeneity of mixtures comprising 10% ethanol
(anhydrous), only at temperatures higher than 0.degree. C. (0.5%
and 2% methyl ester concentration produces near identical results).
Therefore, the performance of depitched tall oil as a solubliser is
far superior to that of canola methyl esters. In this regard, a 2%
concentration of depitched tall oil can maintain a fuel mixture
comprising 10% anhydrous ethanol at temperatures as low as
-15.degree. C. (see FIG. 1).
[0031] When the anhydrous ethanol concentration is increased to
30%, canola methyl esters (up to 6%) will only maintain a
homogeneous solution above 10.degree. C. However, the superior
solublisation properties of depitched tall oil (at 7%) maintain the
same fuel mixture as a homogeneous solution at temperatures as low
as -15.degree. C. (see FIG. 1).
[0032] In conclusion, depitched tall oil exhibits diesel
oil/anhydrous ethanol solublisation properties that are
significantly superior to those of canola methyl esters.
* * * * *