U.S. patent application number 13/468549 was filed with the patent office on 2013-05-16 for diesel microemulsion biofuels.
The applicant listed for this patent is Jacob Issac Abraham, John David McLennan, Thu Thi Le Nguyen, Melisa Saleb Ramallo. Invention is credited to Jacob Issac Abraham, John David McLennan, Thu Thi Le Nguyen, Melisa Saleb Ramallo.
Application Number | 20130118058 13/468549 |
Document ID | / |
Family ID | 48279292 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130118058 |
Kind Code |
A1 |
Nguyen; Thu Thi Le ; et
al. |
May 16, 2013 |
DIESEL MICROEMULSION BIOFUELS
Abstract
A biofuel can include a diesel fuel, a plant oil, an alcohol
viscosity reducer that is either a mixture of a butanol and a
C.sub.1-C.sub.3 alcohol or solely butanol, and a surfactant present
at no more than about 1.0% v/v. The biofuel exists as a clear,
stable microemulsion at from about -10.degree. C. to about
70.degree. C. with the cloud point and pour point lower than
-10.degree. C.
Inventors: |
Nguyen; Thu Thi Le; (Salt
Lake City, UT) ; McLennan; John David; (Salt Lake
City, UT) ; Abraham; Jacob Issac; (Salt Lake City,
UT) ; Ramallo; Melisa Saleb; (Salt Lake City,
UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nguyen; Thu Thi Le
McLennan; John David
Abraham; Jacob Issac
Ramallo; Melisa Saleb |
Salt Lake City
Salt Lake City
Salt Lake City
Salt Lake City |
UT
UT
UT
UT |
US
US
US
US |
|
|
Family ID: |
48279292 |
Appl. No.: |
13/468549 |
Filed: |
May 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61484540 |
May 10, 2011 |
|
|
|
Current U.S.
Class: |
44/302 |
Current CPC
Class: |
C10L 1/1802 20130101;
C10L 1/328 20130101; Y02E 50/13 20130101; C10L 2200/0446 20130101;
C10L 1/1822 20130101; Y02E 50/10 20130101; C10L 1/026 20130101 |
Class at
Publication: |
44/302 |
International
Class: |
C10L 1/18 20060101
C10L001/18 |
Claims
1. A biofuel, comprising: a diesel fuel; a plant oil or derivative
thereof; an alcohol viscosity reducer; and a surfactant present at
no more than about 1.0% v/v, wherein the biofuel exists as a clear,
stable microemulsion at temperatures from about -10.degree. C. to
about 70.degree. C. and has a kinematic viscosity of less than
about 6 cSt at 37.8.degree. C.
2. The biofuel of claim 1, wherein the plant oil is selected from
the group consisting of canola oil, algae oil, jatropha oil,
safflower oil, castor oil, linseed oil, tung oil, soy oil,
sunflower oil, peanut oil, cottonseed oil, palm oil, coconut oil,
rice oil, transesterification product thereof, pyrolysis product
thereof, and combinations thereof.
3. The biofuel of claim 2, wherein the plant oil is canola oil.
4. The biofuel of claim 1, wherein the alcohol viscosity reducer is
an alcohol mixture comprising a butanol and a C.sub.1-C.sub.3
alcohol.
5. The biofuel of claim 4, wherein the C.sub.1-C.sub.3 alcohol is
ethanol.
6. The biofuel of claim 4, wherein the butanol is sec-butanol.
5. The biofuel of claim 4, wherein the butanol is n-butanol.
8. The biofuel of claim 4, wherein the alcohol mixture is present
at from about 12% v/v to about 30% v/v.
6. The biofuel of claim 4, wherein the butanol and the
C.sub.1-C.sub.3 alcohol are present at a ratio of from about 2:1 to
about 6:1.
7. The biofuel of claim 4, wherein the butanol is present at up to
30% v/v.
11. The biofuel of claim 1, wherein the alcohol viscosity reducer
consists essentially of a butanol present at no more than 30%
v/v.
12. The biofuel of claim 1, wherein the surfactant is a fatty acid
having a heating value of from 40 MJ/kg to 46 MJ/kg.
13. The biofuel of claim 1, wherein the surfactant is selected from
the group consisting of oleyl amine, oleyl alcohol, 1-octanol,
ethyl hexyl nitrate, ethyl hexanol, ethylene glycol butyl ether,
and combinations thereof.
14. The biofuel of claim 13, wherein the surfactant comprises
1-octanol.
15. The biofuel of claim 13, wherein the surfactant comprises oleyl
amine.
16. The biofuel of claim 1, wherein the surfactant is present at
from about 0.5% v/v to about 1.0% v/v.
8. The biofuel of claim 1, wherein the diesel fuel is present at
from about 35% v/v to about 99.5% v/v.
9. The biofuel of claim 1, wherein the plant oil and diesel fuel
are present at a ratio of from about 1.0:1.0 to about 1.0:3.0.
10. The biofuel of claim 1, further comprising water at no more
than about 0.5% v/v but greater than 0% v/v.
20. A method of making a biofuel, comprising mixing a diesel fuel,
a plant oil, an alcohol viscosity reducer, and a surfactant at an
amount such that the surfactant constitutes less than 1% v/v of the
biofuel, where the biofuel exists as a clear, stable microemulsion
at from about -10.degree. C. to about 70.degree. C.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/484,540, filed May 10, 2011, which is
incorporated herein by reference.
BACKGROUND
[0002] Over the last several decades, energy shortages and rising
oil and gasoline prices have elevated the interest in
non-petroleum-based renewable fuels. Vegetable oils, particularly
non-food feedstock or inedible vegetable oils, have been considered
for use as renewable fuels. Candidate vegetable oils have been
shown to have similar physical and chemical properties to those of
diesel fuel, and thus have comparable performance in diesel
engines. However, long-term usage of vegetable oils often leads to
engine durability problems. Specifically, such vegetable oil based
fuels exhibit poor atomization of the fuel, injector coking and
ring sticking due to vegetable oil's higher viscosity than typical
diesel fuel. Various studies have reported methods for reducing
vegetable oil viscosity in order to overcome these issues.
Viscosity reduction protocols include transesterification in which
the vegetable oils are chemically converted into their
corresponding fatty acid methyl esters or biodiesels. The viscosity
of such fatty acid methyl esters is reduced by approximately one
order of magnitude. Viscosity of vegetable oils can also be reduced
by pyrolysis, in which triglyceride molecules of vegetable oils are
thermally cracked into mixtures of methyl esters. Alternatively,
viscosity has been reduced by dilution with diesel. However, such
blending introduces difficulties with phase separation, stability
and energy density.
[0003] Factors such as energy content, viscosity, stability and the
like can constrain the types of components that are used in fuel
mixtures. Many fuel additives substantially reduce energy content
or can reduce fuel stability sufficient to make their commercial
use unattractive. Various microemulsions have also been studied,
although such formulations require high surfactant concentrations
in order to maintain phase stability of the fuel. Furthermore,
interactions of various fuel additives with other fuel components
can increase viscosity above industry acceptable standards. As
such, diesel fuel formulations and methods that provide meaningful
viable alternatives to diesel-only fuels continue to be sought.
SUMMARY
[0004] Stable microemulsion biofuels can be achieved which allow
for high fuel stability, low viscosity, and high energy density.
Generally, the biofuel can comprise a diesel fuel, a plant oil,
less than 1.0% v/v surfactant, and an alcohol viscosity reducer
such that the biofuel is a stable microemulsion from about
-10.degree. C. to about 70.degree. C. and has a kinematic viscosity
less than about 6 cSt at 37.8.degree. C. In one formulation, the
diesel biofuel can include a diesel fuel, a plant oil, an alcohol
mixture that includes a butanol and a C.sub.1-C.sub.3 alcohol; and
a total of surfactant present at no more than about 1.0% v/v.
Regardless of the specific components, the diesel biofuel exists as
a clear, stable microemulsion at temperatures from about
-10.degree. C. to about 70.degree. C. over a period of at least 24
hours. In another aspect, the biofuel exhibits a kinematic
viscosity of less than about 6 cSt at 37.8.degree. C. The plant oil
can be selected from the group consisting of canola oil, algae oil,
jatropha oil, safflower oil, castor oil, linseed oil, tung oil, soy
oil, sunflower oil, peanut oil, cottonseed oil, palm oil, coconut
oil, rice oil, although other plant oils can be suitable. In a
specific example, the plant oil is canola oil. In another example,
the C.sub.1-C.sub.3 alcohol is ethanol. The surfactant can be
selected from oleyl amine, oleyl alcohol, 1-octanol, ethyl hexyl
nitrate, ethyl hexanol, ethylene glycol butyl ether, and mixtures
of these surfactants. In particular examples, the surfactant can be
1-octanol, or oleyl amine, or a mixture of these.
[0005] In another embodiment, a biofuel can include a diesel fuel,
a plant oil, no more than 30% v/v of a butanol as the alcohol
viscosity reducer, and no more than about 1.0% v/v of a surfactant
mixture. The biofuel exhibits a kinematic viscosity of less than
about 6 cSt at 37.8.degree. C. In a particular example, the plant
oil and diesel fuel are present at a ratio of from about 1.0:1.0 to
about 1.0:3.0. In another example, the surfactant can be 1-octanol,
or oleyl amine, or a mixture of these.
[0006] A method of making a biofuel can include the mixing of a
diesel fuel, a plant oil, an alcohol mixture, and a surfactant at
an amount such that the surfactant constitutes less than 1% v/v of
the biofuel. The resulting biofuel exists as a clear, stable
microemulsion at temperatures from about -10.degree. C. to about
70.degree. C. This biofuel generally exhibits desirable viscosity,
pour point, cloud point and stability over a wide variation in
temperature. For example, cloud point and pour point can be less
than -10.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a graph of fuel consumption in kg/hr at no load
and 4 lb-ft load conditions for diesel and selected exemplified
biofuel formulations in accordance with specific examples of the
present invention.
[0008] FIG. 2 is a graph of NOx emissions in ppm at no load and 4
lb-ft load conditions for diesel and selected exemplified biofuel
formulations in accordance with specific examples of the present
invention.
[0009] FIG. 3 is a graph of CO emissions in ppm at no load and 4
lb-ft load conditions for diesel and selected exemplified biofuel
formulations in accordance with specific examples of the present
invention.
[0010] FIG. 4 is a graph of SMPS particulate count at no load and 4
lb-ft load conditions for diesel and selected exemplified biofuel
formulations in accordance with specific examples of the present
invention.
[0011] FIG. 5 is a graph of PM10 results at no load and 4 lb-ft
load conditions for diesel and selected exemplified biofuel
formulations in accordance with specific examples of the present
invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0012] In describing embodiments of the present invention, the
following terminology will be used.
[0013] The singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "a surfactant" includes reference to one or
more of such component and "mixing" includes one or more of such
steps.
[0014] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0015] Concentrations, amounts, and other numerical data may be
expressed or presented herein in a range format. It is to be
understood that such a range format is used merely for convenience
and brevity and thus should be interpreted flexibly to include not
only the numerical values explicitly recited as the limits of the
range, but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. As an illustration, a
numerical range of "one to six carbons" should be interpreted to
include not only the explicitly recited values of one carbon and
six carbons, but also include individual values and sub-ranges
within the indicated range. Thus, included in this numerical range
are individual values such as 2, 3, and 4 carbons, and sub-ranges
such as from one to three, from 2 to 5, and from 3 to 6 carbons,
etc. This same principle applies to ranges reciting only one
numerical value and should apply regardless of the breadth of the
range or the characteristics being described.
[0016] As used herein, the term "about" means that dimensions,
sizes, formulations, parameters, shapes and other quantities and
characteristics are not and need not be exact, but may be
approximated and/or larger or smaller, as desired, reflecting
tolerances, conversion factors, rounding off, measurement error and
the like and other factors known to those of skill. Further, unless
otherwise stated, the term "about" shall expressly include
"exactly," consistent with the discussion above regarding ranges
and numerical data.
[0017] The term "viscosity" as used herein refers generally to a
degree of resistance to flow exhibited by a fluid. There are a
number of methods of measuring viscosity recognized in the art,
which may be based on different underlying physical variables. As
used herein in reference to fuel compositions, "viscosity" refers
to kinematic viscosity unless otherwise indicated. Units reported
for kinematic viscosity will be cSt.
[0018] Microemulsion fuels are clear, low-viscosity, stable
dispersions which typically contain a continuous hydrocarbon phase
and a discontinuous polar phase. These dispersions can be
stabilized by surfactant films and tend to appear isotropic due to
the small droplet size (<100 nm) of the equilibrated reverse
micelles. Microemulsion fuels have several advantages. For example,
microemulsion fuels have been shown to reduce soot formation,
NO.sub.x and CO emission. Microemulsion fuels can also improve fuel
atomization and increase the fuel flash point, which is
advantageous for storage. Preparation of these microemulsions can
also involve simple mechanical mixing with little or no reaction.
As such, implementation and production can be achieved with low
capital costs and maintenance.
[0019] Diesel-based fuels can be extended by replacing some of the
diesel with other components such as plant oils (e.g. vegetable
oils). Plant oils are of interest as an alternative to diesel fuel
due to their comparable properties and performance to diesel fuel.
However, their high viscosity causes engine durability problems
after long-term usage. As described herein, vegetable oil viscosity
can be reduced by blending the plant oil with diesel fuel in
thermodynamically stable mixtures via a microemulsion fuel
formulation. In accordance with the present innovation, a method of
making a microemulsion biofuel involves the mixing of two
immiscible fluids, i.e. a water/short chain alcohol viscosity
reducer and a diesel/vegetable oil mixture, to reduce the viscosity
of vegetable oil by the aid of surfactants that stabilize the
mixture.
[0020] In one embodiment, the diesel biofuel can comprise a diesel
fuel, a plant oil, an alcohol viscosity reducer, and a very low
level of surfactant. The alcohol viscosity reducer can be an
alcohol mixture comprising a butanol and a C.sub.1-C.sub.3 alcohol.
Alternatively, the alcohol viscosity reducer can be solely a
butanol. In one aspect, the stability of the microemulsion biofuels
is enhanced and the viscosity is reduced while still maintaining
advantageous characteristics by using surfactants to incorporate a
short-chain alcohol in the mixtures of diesel and plant oil.
[0021] According to the embodiment, the biofuel can include any
type of liquid diesel fuel, including petroleum diesel, synthetic
diesel and biodiesel. In a particular example, the diesel fuel is a
petroleum diesel. The diesel fuel that can be used in the present
biofuel is not limited to any particular grade. In a particular
example, any grade of diesel fuel available for use in vehicle
engines, e.g. grades of No. 1, No. 2, and No. 4 diesel, can be
used. In a particular embodiment, the amount of diesel present can
be from about 35% v/v to about 99.5% v/v. Synthetic diesel can be
formed by conversion of hydrocarbon fuels or natural gas into
diesel fuel.
[0022] In addition to diesel, the biofuel can comprise an amount of
plant oil. The plant oil can be of any kind, without limitation. In
particular, the fuel can include one or more plant oils from crop
sources that are not used for human consumption. Examples of
suitable plant oils include but are not limited to canola oil,
algae oil, jatropha oil, safflower oil, castor oil, linseed oil,
tung oil, soy oil, sunflower oil, peanut oil, cottonseed oil, palm
oil, coconut oil, rice oil, combinations thereof, and
transesterification products or pyrolysis products thereof. In a
specific example, the plant oil is canola oil.
[0023] Plant oil can be included to provide energy content to the
biofuel as a replacement for an amount of diesel. The total amount
of plant oil, as well as the relative amount of diesel and plant
oil, can be selected based on the desired properties of the
biofuel. Generally speaking, plant oils tend to be relatively
viscous, and increasing the amount of plant oil in a fuel mixture
can therefore increase the viscosity of the fuel. In biofuels
according to the present technology, however, viscosity is reduced
by mixing the diesel/plant oil mixture with one or more short-chain
alcohols. In one aspect, this approach allows for the inclusion of
greater amounts of plant oils in a biofuel than would otherwise be
possible without exceeding practical limits on viscosity for a
given type of fuel. In a particular embodiment, the biofuel
contains plant oil at from about 20% v/v to about 45% v/v. In
another embodiment, plant oil and diesel fuel are present in the
biofuel at a ratio of from about 2.0:1.0 to about 1.0:3.0.
Viscosity can also be reduced by transesterification or pyrolysis
of the plant oil to produce smaller derivative compounds having a
lower viscosity.
[0024] In accordance with one embodiment, a mixture of at least two
alcohols is included in the biofuel. More specifically, this
alcohol mixture can comprise two short-chain alcohols. In a
particular embodiment, one of the alcohols in the alcohol mixture
is a butanol. In one specific example, the butanol in the mixture
is sec-butanol. In another specific example, the butanol is
n-butanol. Non-limiting examples of butanols can include n-butanol,
sec-butanol, isobutanol, tert-butanol, mixtures of these, and the
like. In another aspect, the alcohol mixture includes a short chain
alcohol having a chain length of C.sub.1 to C.sub.3, such as
methanol, ethanol, n-propanol, isopropanol or mixture of these. In
a specific example, the short chain alcohol is ethanol. In one
particular embodiment, the alcohol mixture used in the biofuel is a
mixture of a butanol and ethanol. The alcohols can be anhydrous, or
alternatively can include some water. For example, the ethanol used
can be 95% ethanol with remainder water. In one aspect, both of the
alcohols act as viscosity reducers in the biofuel. In another
aspect, the alcohols also contribute to maintenance of the energy
content of the biofuel. Therefore, the combination of alcohols
selected may provide a balance between these two aspects. For
example, the viscosity of ethanol is lower than that of butanol,
while butanol has higher energy content than ethanol. Therefore,
both ethanol and butanol can be used in the microemulsion biofuel
preparation for the purposes of obtaining a desirable viscosity
without unduly lowering the energy content of the fuel. As follows
from these examples, the biofuel can include a mixture of two,
three, or more alcohols to contribute characteristics of viscosity
reduction, energy content, or other characteristics to the
fuel.
[0025] According to another embodiment, a butanol can constitute
the sole alcohol in the biofuel. This approach takes advantage of
the higher energy content of butanol. In a specific example, the
butanol can be present at up to 30% v/v of the fuel. The biofuel
according to this embodiment can exhibit a desirable viscosity,
e.g. less than 6.0 cSt at 37.8.degree. C. and often from about 1.9
cSt to about 6.0 cSt. In an aspect of this embodiment, somewhat
less plant oil may be included in order to maintain this viscosity.
For example, in such a biofuel plant oil and diesel fuel can be
present at a ratio of from about 1.0:1.0 to about 1.0:3.0.
[0026] The total alcohol mixture or individual alcohols can be
included in the biofuel in amounts that provide a particular
viscosity with respect to the diesel/plant oil makeup present. In
an embodiment, the total alcohol mixture is present at from about
12% v/v to about 30% v/v. In another aspect, the relative amounts
of individual alcohols in a particular mixture can be selected to
provide a given combination of viscosity reduction and energy
content. In an embodiment, the alcohol mixture comprises butanol
and a C.sub.1-C.sub.3 alcohol at a ratio of from about 2:1 to about
6:1. Ratios close to 1:1 tend to phase separate.
[0027] According to the present technology, low-viscosity biofuels
can be made by combining diesel, plant oil, and a specific alcohol
mixture. In particular, these fuels can include significant amounts
of plant oils while exhibiting viscosities that meet accepted
requirements for use in diesel engines. For example, fuel viscosity
can affect injector lubrication and fuel atomization. That is,
fuels with low viscosity may not provide sufficient lubrication for
the precision fit of fuel injection pumps or injector plungers,
resulting in leakage or increased wear. As such, the diesel biofuel
formulation can have a viscosity greater than about 1.9 cSt at
37.8.degree. C. Furthermore, bio-based diesel fuels with high
viscosity tend to form larger droplets on injection which can cause
poor combustion and increased exhaust smoke and emissions. In a
particular aspect, the present biofuels exhibit viscosities of less
than 6.0 cSt at 37.8.degree. C.
[0028] The biofuels according to the present technology can also be
stable microemulsions. These dispersions can be stabilized using
surfactants. Surfactants can optionally be excluded from the
formulation, for example, if the fuel is used quickly within less
than three to four weeks, or less than four days, depending on the
specific formulation. However, for commercial operations, plant
oil-based fuel microemulsions typically involve the use of
significant amounts of surfactant for stability. This requirement
can increase the resource costs associated with production of such
fuels. Furthermore, the presence of high levels of surfactants can
cause maintenance problems in diesel engines. Notably, biofuels
according to the present technology exhibit considerable stability
while employing very low amounts of surfactant. In one embodiment,
the biofuel includes surfactant at no more than about 1.0% v/v but
above 0% v/v. In a more specific embodiment, the biofuel can
include surfactant at from about 0.5% to about 1.0% v/v, and in
some cases no less than about 0.05% v/v surfactant. The present
biofuel exhibits considerable stability over a wide range of
temperatures. In a particular example, the biofuel is clear and
stable at from about -10.degree. C. to about 70.degree. C.
Typically, the biofuel can have a cloud point of 40.degree. F. or
lower. In another aspect, the biofuel can have a pour point from
about 15.degree. F. to about 20.degree. F. One embodiment of the
present biofuel has a cloud point and a pour point lower than
-10.degree. C.
[0029] The biofuel can include any surfactants that are suitable
for use in fuels. In particular, hydrophobic surfactants, which
tend to form reverse micelles, are indicated for use in this type
of microemulsion fuel, and such surfactants are also suitable for
use in the present biofuels. Specifically, these fuels can be
reverse micellar microemulsion type, in which the continuous phase
is the oil (e.g. diesel and canola oil) and the dispersed phase is
reverse micellar droplets of water and short chain alcohol. In
order to form a reverse micellar microemulsion, the surfactants
tend to be hydrophobic since they prefer the hydrophobic oil phase
more than hydrophilic surfactants. The selection of surfactant can
be based on other contributions to fuel properties. For example,
surfactants with fatty acid chains having a sufficiently high
heating value can be used in the present biofuels, particularly
those having heating values similar to conventional diesel fuel
(e.g. 44 MJ/kg). In a specific embodiment, the surfactant is a
fatty acid having a heating value of from 40 MJ/kg (such as lauric
acid C12) to 46 MJ/kg (such as oleic acid C18). In another aspect,
surfactants that enhance the cetane number of fuels, e.g. alkyl
amines, can also be used. In a particular embodiment, the
surfactant includes at least one of oleyl alcohol, oleyl amine,
1-octanol, ethyl hexyl nitrate, ethyl hexanol, ethylene glycol
butyl ether and combinations thereof. In one specific embodiment,
the surfactant comprises oleyl amine. In another specific
embodiment, the surfactant comprises 1-octanol.
[0030] In another embodiment, the biofuel can include a surfactant
mixture comprising a surfactant and one or more cosurfactants. In a
specific example, the surfactant is a mixture of 1-octanol and
oleyl amine. Other non-limiting surfactant combinations include
oleyl alcohol and 1-octanol, oleyl amine or oleyl alcohol and one
or two of the cosurfactants including 1-octanol, ethyl hexyl
nitrate, ethyl hexanol, ethylene glycol butyl ether, and the like.
Where a surfactant mixture is used in biofuels according to the
present concept, the ratio of constituent surfactant amounts is not
particularly limited. Any ratios of surfactants that can provide
the viscosity and stability as described herein with the present
biofuels, particularly within the total surfactant amounts
described herein can be suitable. The ratio employed can be
selected based on a desired contribution of individual surfactants
to the fuel's properties, such as cetane number or heating
value.
[0031] The present biofuels can also include a small amount of
water. The presence of water in microemulsion fuel can reduce
emission of NO and particulates. The water in the fuel may be
present by deliberate addition. Alternatively, the biofuel can
include water as a byproduct of steps in the production process or
be introduced by the addition of particular components. In a
particular embodiment, the biofuel can include water at 0.5% v/v or
less (i.e. but not zero). Short chain alcohols such as ethanol and
methanol can provide a similar effect (i.e. reducing emission of
NO.sub.x, CO and particulates) as water due to their lower
combustion temperature than that of diesel fuel.
[0032] In accordance with an embodiment, a method of making a
stable microemulsion biofuel can comprise mixing together a diesel
fuel, a plant oil, an alcohol mixture comprising short chain
alcohols, and a surfactant mixture (including cosurfactants) at an
amount such that the surfactant constitutes less than 1% v/v of the
biofuel. In a particular embodiment, the alcohol mixture includes a
butanol and a C.sub.1-C.sub.3 alcohol. Microemulsions typically
form spontaneously with slight mixing of these components.
Accordingly, the present microemulsion biofuels can be prepared by
direct mixing of all of the components using mixing equipment
suited for such purposes, e.g. a continuous stirred tank
reactor.
EXAMPLES
Testing the Effect of Varying Ethanol/Butanol Ratio in
Microemulsion Biofuels
[0033] Microemulsion biofuels were formulated using the components
listed in Table 1 below. Consumer grade canola oil and No. 2 diesel
were obtained from local retailers. Ethanol Proof 190 (95%
ethanol), sec-butanol, 1-octanol (100% active) and oleyl amine (70%
active) purchased from Sigma-Aldrich Corporation, St. Louis, Mo.,
were used as renewable viscosity reducers. Deionized water was used
in all formulations, recognizing a potential modification to
surfactant blends from other water sources (such as tap water with
hardness).
[0034] All fuel ingredients were added together by volume using
volumetric cylinders. The 2-butanol and ethanol were the last
components to be added in the fuel to minimize evaporation of these
components during preparation. The biofuels were then gently
hand-shaken at room temperature to obtain clear and homogenous
microemulsion upon mixing. Each sample was then stored at a
constant temperature ranging from -10.degree. C. to 70.degree. C.
in temperature increments of 20.degree. C. (in a freezer or a
heating water bath). The biofuels were maintained at each testing
temperature for 24 hours before they were observed for any phase
separation. For the biofuels without any phase separation at all
testing temperatures (Table 1), the viscosity was measured at
37.8.degree. C. and 54.4.degree. C. using a TA Instrument AR550
Rheometer. For each example, viscosity measurement was done in
triplicate at 37.8 and 54.4.degree. C. The average value was
reported at each temperature. The coefficient of variation was less
than 10%. The kinematic viscosity was calculated from the measured
dynamic viscosity and the density of the fuel at the corresponding
temperatures. The density of the fuel was measured at 37.8 and
54.4.degree. C. using an Anton Paar mPDS 2000 Density Meter.
[0035] The cloud point (the temperature at which the fuel begins to
thicken and becomes cloudy) and pour points (the temperature at
which begins to thicken and no longer pours) of selected biofuels
were determined. The standard cloud point for diesel No. 2 in
winter weather (November through February) is -10.degree. C. max
and in summer weather (March through October) is -4.degree. C. The
standard pour point for No. 2 diesel fuel is -17.8.degree. C. and
-9.4.degree. C. in winter and summer weathers, respectively. The
pour point of the biofuel was measured using a TA Instruments AR550
Rheometer. The cloud point was measured following ASTM D2500, in
which the biofuel was observed for the first sign of turbidity and
cloudiness in a cooling water bath as the temperature was decreased
at intervals of 5.degree. C. The final blends developed were
observed to thicken and become cloudy at -10.degree. C. At the
other end of the spectrum, phase separation was not observed at
temperatures up to 70.degree. C.
[0036] The differences between biofuel Examples 1 through 3 shown
in Table 1 are that ethanol and butanol were included in three
different ratios with a combined concentration of 30%. The
kinematic viscosity was measured and was within an acceptable
range.
TABLE-US-00001 TABLE 1 Composition (in v/v %) of microemulsion
fuels in which the ethanol/butanol ratio is varied. Examples 1 2 3
Diesel 35 35 35 Canola oil 35 35 35 Ethanol 95% 0 5 10 Sec-butanol
30 25 20 1-octanol 0.5 0.5 0.5 Oleyl amine 0.35 0.35 0.35 Water
0.15 0.15 0.15 Viscosity (cSt) at 37.8.degree. C. 4.57 4.35 4.12
54.4.degree. C. 3.25 3.12 3.02
[0037] Table 1 shows microemulsions that were stable and did not
show phase separation after 24 hours between -10.degree. C. and
70.degree. C. It was found that phase separation occurs at an
ethanol to butanol ratio of 1:1. As the portion of butanol is
increased, for example, at ethanol to butanol ratio of 1:2 and 1:5,
no phase separation occurs and the fuel viscosity is still within
an acceptable range of 1.9-6 cSt. As the ratio of ethanol to
sec-butanol increases, the viscosity of the microemulsion fuel
decreases at both testing temperatures (37.8 and 54.4.degree. C.)
due to the lower viscosity of ethanol compared to sec-butanol.
However, we found that the fuel without ethanol and with 30% of
butanol still maintained a desirable fuel viscosity.
Testing the Effect of Varying Total Alcohol Amount
[0038] Microemulsion biofuels were formulated by the process of
Examples 1 through 3 above, using the components listed in Table 2.
In biofuel Examples 4 through 7, ethanol and butanol were included
to give three different total alcohol levels, and the kinematic
viscosity for each was measured. The ratio of ethanol to
sec-butanol was maintained at 1:2.
TABLE-US-00002 TABLE 2 Composition (in v/v %) of microemulsion
fuels in which total composition of ethanol and butanol is varied.
Examples 4 5 6 7 Diesel 35 38 41 44 Canola oil 35 38 41 44 Ethanol
95% 10 8 6 4 Sec-butanol 20 16 12 8 1-octanol 0.5 0.5 0.5 0.5 Oleyl
amine 0.35 0.35 0.35 0.35 Water 0.15 0.15 0.15 0.15 Viscosity (cSt)
at 37.8.degree. C. 4.13 4.70 5.25 6.81 54.4.degree. C. 3.02 3.24
4.37 5.03
[0039] The minimum total composition of ethanol and butanol for the
microemulsion fuels to obtain desirable viscosity was determined to
be 12 v/v %, as shown in Table 2. The maximum total composition of
ethanol and butanol was kept at 30 v/v %. Previous studies showed
that higher compositions of ethanol and/or butanol in the fuel have
greatly reduced the efficiency of the fuels. The viscosity of the
microemulsion fuels increases as the concentration of ethanol and
sec-butanol decreases.
Testing the Effect of Varying Total Surfactant Concentration
[0040] Microemulsion biofuels were formulated by the process of
Examples 1 through 3 above, but using the components listed in
Table 3. In biofuel Examples 8 through 11 oleyl amine and 1-octanol
were included to give three different total surfactant levels. The
1-octanol/oleyl amine ratio was held at 1.0/0.7 by volume. The
1-octanol has fuel improving effects, while long chain oleyl amine
surfactant has a similar heating value to that of diesel and can
also act as a cetane enhancer due to the presence of the amine
group in the molecule. The amount of water was also varied to keep
the volume of water and surfactant/cosurfactant at 2% v/v. The
kinematic viscosity for each resulting fuel was measured. As shown
in Table 3, as low as only 0.425 v/v % of total surfactant
concentration was needed to achieve microemulsion stability.
TABLE-US-00003 TABLE 3 Composition (in v/v %) of microemulsion
fuels in which total surfactant concentration is varied. Examples 8
9 10 11 Diesel 34 34 35 35 Canola oil 34 34 35 35 Ethanol 95% 5 5 5
5 Sec-butanol 25 25 25 25 1-octanol 1.5 1 0.5 0.25 Oleyl amine 1.05
0.7 0.35 0.175 Water 0.45 0.3 0.15 0.075 Viscosity (cSt) at
37.8.degree. C. 4.31 4.26 4.35 4.29 54.4.degree. C. 3.26 3.23 3.12
3.19
[0041] These results demonstrate that the total surfactant
concentration has very little effect on the viscosity of the
microemulsion biofuels.
Testing the Effect of Varying 1-Octanol/Oleyl Amine Ratio
[0042] Microemulsion biofuels were formulated by the process of
Examples 1 through 3 above, but using the components listed in
Table 4 below. In biofuel Examples 12 through 16, the ratio of
1-octanol/oleyl amine was varied to determine its effect on the
stability and viscosity of the microemulsion fuels. Water was added
to maintain the ratio between the concentration of total surfactant
and water at 1.0%.
TABLE-US-00004 TABLE 4 Composition (in v/v %) of microemulsion
fuels in which 1-octanol/oleyl amine ratio is varied. Examples 12
13 14 15 16 Diesel 44 44 44 44 44 Canola oil 44 44 44 44 44 Ethanol
95% 4 4 4 4 4 Sec-butanol 8 8 8 8 8 1-octanol 0 0.3 0.5 0.7 1.0
Oleyl amine 0.7 0.49 0.35 0.21 0 Water 0.3 0.21 0.15 0.09 0
Viscosity (cSt) at 37.8.degree. C. 6.97 6.82 6.81 6.61 6.87
54.4.degree. C. 5.15 5.09 5.03 4.98 5.09
[0043] The microemulsion fuels were stable at all 1-octanol/oleyl
amine ratios. Furthermore, the viscosity of the fuels was not much
affected by the variation of the surfactant ratio.
Testing the Effect of Varying Diesel/Canola Oil Ratio
[0044] Microemulsion biofuels were formulated by the process of
Examples 1 through 3 above, but using the components listed in
Table 5 below. In biofuel Examples 17 through 19, the ratio of
diesel and canola oil was varied. Other parameters were maintained
constant and the kinematic viscosity for each resulting fuel was
measured.
TABLE-US-00005 TABLE 5 Composition (in v/v %) of microemulsion
fuels in which diesel/canola ratio is varied. Examples 17 18 19
Diesel 61 44 31 Canola oil 27 44 57 Ethanol 95% 4 4 4 Sec-butanol 8
8 8 1-octanol 0.5 0.5 0.5 Oleyl amine 0.35 0.35 0.35 Water 0.15
0.15 0.15 Viscosity (cSt) at 37.8.degree. C. 4.58 6.81 9.22
54.4.degree. C. 3.47 5.03 6.38
[0045] The microemulsion fuels retained stability over a
temperature range from -10.degree. C. to 70.degree. C. However, the
viscosity increased as the diesel/canola ratio was decreased.
[0046] All of the microemulsion fuel formulations reported in
Tables 1 through 5 showed no phase separation within a temperature
range of -10.degree. C. to 70.degree. C. over a period of 48 hours.
The experimental results show that at the total
surfactant/cosurfactant concentration lower than 0.4 v/v %, phase
separation occurs. The cloud points and pour points for all of the
reported formulations were lower than -10.degree. C.
Testing of Cloud Point and Pour Point of the Biofuel
[0047] The cloud point is the temperature at which the fuel begins
to thicken and become cloudy. The pour point is the temperature at
which the fuel begins to thicken and no longer pours. The cloud
point and pour point are important properties of fuels since at the
cloud point, some engines fail to run and at the pour point, all
engines fail to run. The cloud point and pour point of the biofuels
were determined based on the observation of the biofuels to thicken
and become cloudy at cold temperature as they are cold properties
of the fuels in accordance with ASTM D2500 and ASTM D975,
respectively. The microemulsion fuels prepared have cloud points
and pour points both lower than -10.degree. C. This meets the
accepted requirements for diesel engines (cloud point of 45.degree.
F. and pour point of 15-20.degree. F.). The ability of biofuels to
function at low temperatures is a consideration in regions with
seasonal climatic extremes.
Testing of Performance of the Biofuels in an Instrumented Diesel
Engine
[0048] From the matrix of blends described above, biofuels with a
kinematic viscosity less than 6.0 cSt at 37.8.degree. C. were run
in an instrumented Kubota 482 cc diesel engine at the University of
Utah. No. 2 diesel fuel was also run under the same operating
conditions for baseline performance and emission comparisons. Two
engine conditions were tested: an idle condition and a scenario
representing running at high load conditions. Fuel was gravity fed
to the engine from a platform with a digital scale so that fuel
consumption could be gravimetrically determined. Exhaust from this
engine was sent directly to a Model 300 California Analytical
CO/CO.sub.2 analyzer and a Thermo Electron Chemiluminescence NOx
analyzer and gas concentration (in ppm) was continuously recorded.
Exhaust gas was also sent to an eductor and a dilution manifold
from which samples were drawn and analyzed by a TSI DustTrak PM 10
monitor and a TSI Scanning Mobility Particle Sizer (SMPS) to
determine the exhausted particle size distribution and
concentration. The DustTrak PM 10 provides a mass-based measurement
of particulate matter (PM) with a diameter of 10 microns or less
(PM 10) while the SMPS senses particle sizes ranging from 14 to 720
nm.
[0049] The mass of the fuel was recorded before and after each test
run, yielding average fuel consumption. Before each test, the
siphon line was drained and the new fuel to be tested was flushed
through the functioning engine for .about.5 minutes. The engine was
set at two conditions for each fuel: no load at 1500 rpm and 4
ft-lb at 2200 rpm. At each loading condition, the engine was run
for 30 minutes for each fuel after the five-minute flushing period.
All gas and particle data were continuously recorded.
[0050] FIG. 1 shows the fuel consumption for diesel (baseline) and
for selected microemulsion fuels at the two engine conditions. The
ordinate designates consumption in kg/hour and the abscissa
indicates the microemulsion formulation, as designated in Tables 1
through 5. As anticipated, for all fuels the fuel consumption is
much lower at no-load conditions than under high-load conditions.
Microemulsion fuel consumption is universally higher than diesel at
both conditions, specifically from about 9-23% and 6-20% higher at
no-load and high-load conditions, respectively. This is due to the
presence of short chain alcohols, which have much lower energy
content than diesel fuel, in the microemulsion fuels.
[0051] Microemulsion fuel formulations 3, 4, 5 and 6 have a
progressively decreasing concentration of ethanol and sec-butanol
(see Table 2). As the total ethanol and sec-butanol concentration
decreases from 30% (Formulation 3) to 12% (Formulation 6), fuel
consumption decreases. Microemulsion fuel formulations 6, 14 and 15
(61/26 to 44/44 to 31/57, respectively) have varying ratios of
diesel to canola oil (see Table 5). At no-load conditions, the fuel
consumption was nominally unaffected by the studied diesel/canola
oil ratio. However, under high-load condition, as the diesel/canola
oil decreases from 61/26 to 44/44 to 31/57, fuel consumption
increases from 3.6 to 3.8 to 4.0 kg/hr (diesel was 3.4 kg/hour).
The lower cetane number and the lower heat content of canola oil,
as compared to diesel fuel cause this fuel consumption to increase
with an increasing amount of canola oil in the microemulsion
fuel.
[0052] The NOx emissions were also measured. These are compared in
FIG. 2. Similar trends in the NOx emission were observed under
no-load and high-load conditions. Under no-load condition, NOx
emission from all of the microemulsion fuels did not exceed of the
baseline for No. 2 diesel. Under high-load condition, emission
relative to diesel was variable--some higher and some lower. As the
total concentration of ethanol and sec-butanol decreases from 30%
in Formulation 3 to 12% in Formulation 6, NOx emissions increase.
For Formulations 6, 10 and 13 (see Table 4), as the ratio of
1-octanol to oleyl amine increases, NOx emissions decrease
slightly. It was observed that NOx emissions were not affected by
varying ratios of diesel and canola oil in the fuel (Formulations
6, 14 and 15). From these limited data, it appears that NOx
emission is reduced by replacing a portion of the diesel by short
chain alcohols (which also act as viscosity reducers) and by
increasing the concentration of cetane number improver in the
fuel.
[0053] FIG. 3 shows the CO emissions from No. 2 diesel fuel and the
tested microemulsion fuels. CO emissions from the microemulsion
fuels are significantly larger than for the diesel at no-load
conditions. CO emissions only slightly increase or remain the same
at high-load conditions. For the microemulsion fuels with a 30%
total ethanol/sec-butanol concentration (Formulations 1, 2, 3 and
9), carbon monoxide emissions are higher than for the other
microemulsion fuels which have lower concentrations of ethanol and
sec-butanol. CO emissions decreases more obviously as the ethanol
and sec-butanol concentrations decrease under no-load running
conditions (Formulations 3, 4, 5 and 6, see Table 2).
[0054] Particle emissions from diesel combustion exhaust constitute
some fraction of the air pollution that has been implicated in
human heart and lung damage. The exposure to PM 10 (particles with
a diameter of 10 .mu.m or less) can pose major concern for human
health. To assess this risk, particle emissions (FIG. 4) and PM 10
emissions (FIG. 5) were measured and compared for the diesel and
microemulsion fuels used in the engine tests. FIG. 4 shows the
recorded particle counts 14 to 720 nm in the exhaust from engine
tests. As the concentration of ethanol and sec-butanol decreases to
24% and less (the remaining microemulsion fuels), the particle
count measured for the microemulsion fuels significantly decreases.
The particulate matter reduces as ethanol and sec-butanol are added
because of their oxygen content of ethanol and sec-butanol. Most of
the microemulsion fuels have PM 10 emission that meets the EPA's
health-based national air quality standard of 150 .mu.g/m.sup.3
daily concentration.
[0055] For the idle conditions in this particular laboratory-scale
engine, the fuel consumption of the biofuels is higher than that of
No. 2 diesel fuel by about 7.5% to about 23%. The NO.sub.x emission
is lowered by up to about 37%, although it increased for those with
30% alcohol. The CO emission is higher for all of the biofuels.
Compared to No. 2 diesel fuel, the biofuels emitted particulates
with a higher total concentration than No. 2 diesel fuel alone, but
PM 10 (particulate matters with diameter of 10 micron or less)
concentration of 20 to 74% lower depending on formulations.
[0056] For running at high load conditions (i.e. 4 lb-ft at 2200
rpm) in the particular instrumented motor, biofuel consumption is
higher than that of No. 2 diesel fuel by about 5.6% to about 20%
while the NO.sub.x and CO emissions are lowered by up to about 16%
and 6%, respectively. Compared to No. 2 diesel fuel, the biofuels
with alcohol concentration of 24% or less emit particulates with
concentration of 23 to 67% lower and PM 10 concentration of 36 to
93% lower for all of the biofuels.
[0057] While the forgoing examples are illustrative of the
principles of the present invention in one or more particular
applications, it will be apparent to those of ordinary skill in the
art that numerous modifications in form, usage and details of
implementation can be made without the exercise of inventive
faculty, and without departing from the principles and concepts of
the invention. Accordingly, it is not intended that the invention
be limited, except as by the claims set forth below.
* * * * *