U.S. patent application number 10/871116 was filed with the patent office on 2005-01-06 for hydrocarbon fuel with improved laminar burning velocity and method of making.
Invention is credited to Farrell, John T., Johnston, Robert J..
Application Number | 20050000855 10/871116 |
Document ID | / |
Family ID | 33555768 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050000855 |
Kind Code |
A1 |
Farrell, John T. ; et
al. |
January 6, 2005 |
Hydrocarbon fuel with improved laminar burning velocity and method
of making
Abstract
A hydrocarbon fuel such as a gasoline exhibiting substantially
improved laminar burning velocity and method of making. The
hydrocarbon fuel may comprise a paraffinic fraction, an olefinic
fraction, and an aromatics fraction. The aromatics fraction may
comprise methyl aromatics and non-methyl alkyl aromatics wherein
the percentage of non-methyl alkyl aromatics in the aromatics
fraction is at least 30% by volume. The fuel may comprise a methyl
aromatics fraction comprising xylenes wherein the percentage of
ortho- and para-xylene in the xylene fraction is at least 60% by
volume.
Inventors: |
Farrell, John T.; (High
Bridge, NJ) ; Johnston, Robert J.; (Bridgewater,
NJ) |
Correspondence
Address: |
ExxonMobil Research and Engineering Company
P.O. Box 900
Annandale
NJ
08801-0900
US
|
Family ID: |
33555768 |
Appl. No.: |
10/871116 |
Filed: |
June 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60485001 |
Jul 3, 2003 |
|
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Current U.S.
Class: |
208/16 ;
585/14 |
Current CPC
Class: |
C10L 1/06 20130101; C10L
1/1608 20130101 |
Class at
Publication: |
208/016 ;
585/014 |
International
Class: |
C10L 001/06 |
Claims
What is claimed is:
1. An unleaded hydrocarbon fuel comprising a paraffinic fraction,
an olefinic fraction, and an aromatics fraction, wherein said
aromatics fraction comprises methyl aromatics and non-methyl alkyl
aromatics and the percentage of non-methyl alkyl aromatics in said
aromatics fraction is at least 30% by volume.
2. The hydrocarbon fuel of claim 1, wherein said paraffinic
fraction is in an amount of 90% or less by volume, said olefinic
fraction is in an amount of 30% or less by volume, and said
aromatics fraction is in an amount of 70% or less by volume.
3. The hydrocarbon fuel of claim 1, wherein the percentage of
non-methyl alkyl aromatics in said aromatics fraction is at least
50% by volume.
4. The hydrocarbon fuel of claim 1, wherein the percentage of
non-methyl alkyl aromatics in said aromatics fraction is at least
70% by volume.
5. The hydrocarbon fuel of claim 1, wherein said methyl aromatics
fraction comprises xylenes and the percentage of ortho- and
para-xylene in said xylene fraction is at least 60% by volume.
6. The hydrocarbon fuel of claim 1, wherein said methyl aromatics
fraction comprises xylenes and the percentage of ortho- and
para-xylene in said xylene fraction is at least 75% by volume.
7. The hydrocarbon fuel of claim 1, wherein said methyl aromatics
fraction comprises xylenes and the percentage of ortho- and
para-xylene in said xylene fraction is at least 90% by volume.
8. The hydrocarbon fuel of claim 1, further comprising benzene in
an amount of 1% or less by volume, and sulfur in an amount of 30
ppm or less by weight.
9. An unleaded hydrocarbon fuel comprising a paraffinic fraction,
an olefinic fraction, and an aromatics fraction, wherein said
aromatics fraction comprises a xylene fraction and wherein the
percentage of ortho- and para-xylene in said xylene fraction is at
least 60% by volume.
10. The hydrocarbon fuel of claim 9, wherein the percentage of
ortho- and para-xylene in said xylene fraction is at least 75% by
volume.
11. The hydrocarbon fuel of claim 9, wherein the percentage of
ortho- and para-xylene in said xylene fraction is at least 90% by
volume.
12. The hydrocarbon fuel of claim 9, further comprising benzene in
an amount 1% or less by volume, and sulfur in an amount of 30 ppm
or less by weight.
13. A method for making a hydrocarbon fuel having an improved
laminar burning velocity the method comprising: providing a
hydrocarbon fuel comprising a paraffinic fraction, an olefinic
fraction, and an aromatic fraction wherein said aromatic fraction
comprises methyl aromatics and non-methyl alkyl aromatics; and
controlling the percentage of said non-methyl alkyl aromatics in
said aromatics fraction to at least 30% by volume.
14. The method of claim 13, further comprising controlling the
percentage said of non-methyl alkyl aromatics in said aromatics
fraction to at least 50% by volume.
15. The method of claim 13, further comprising controlling said
percentage of said non-methyl alkyl aromatics in said aromatics
fraction to at least 70% by volume.
16. A method for making a hydrocarbon fuel having an improved
laminar burning velocity the method comprising providing a
hydrocarbon fuel comprising a paraffinic fraction, an olefinic
fraction, and an aromatic fraction comprising methyl aromatics and
non-methyl alkyl aromatics, wherein said methyl aromatics fraction
comprises xylenes; and controlling the percentage of ortho- and
para-xylene in the xylene fraction to at least 60% by volume.
17. The method of claim 16, further comprising controlling the
percentage of ortho- and para-xylene in the xylene fraction to at
least 75% by volume.
18. The method of claim 16, further comprising controlling the
percentage of ortho- and para-xylene in the xylene fraction to at
least 90% by volume.
Description
[0001] This application claims the benefit of U.S. Ser. No.
60/485,001 filed Jul. 3, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to an improved. hydrocarbon
fuel and method for making it. More specifically, it relates to a
hydrocarbon fuel exhibiting improved laminar burning velocity. The
improved hydrocarbon fuel substantially increases engine
efficiency.
BACKGROUND OF THE INVENTION
[0003] Increasingly more stringent emissions and efficiency
regulations pose a significant hurdle to internal combustion engine
makers. Current spark ignition and compression ignition engine
efficiencies are well below the theoretical maxima, and even small
efficiency improvements are highly desirable. Many engine makers
are developing sophisticated hardware controls to extract more
efficiency from the combustion cycle. For example, techniques such
as direct injection, homogeneous charge compression ignition,
variable valve timing, and turbocharging have been commercialized
to varying levels, and have proved successful in improving
efficiency. The effects of fuel composition on engine efficiency
have also been actively studied. Presently, a fuel's octane number
is considered to have the most significant impact on engine
efficiency, since higher octane number fuels allow a closer
approach to optimum spark advance timing and permit increased
compression ratio operation. The effects of the fuel's laminar
burning velocity (or the closely related laminar flame speed) on
engine efficiency have also been studied but are not as well
understood. It is generally recognized that faster burn rates in
engines lead to higher efficiency. For this reason there has been a
trend in engine designs in recent years to modify the mechanical
design of the fuel system and/or combustion chamber (e.g.,
increased swirl and/or tumble) to enhance burn rates. Engine
correlation tools developed to predict burn rates traditionally
incorporate the fuel's laminar flame speed (SAE800133). Further, it
has been shown that increases in engine burn rates in a modern lean
burn type engine correlate directly with increases in fuel laminar
flame speed measurements made in a constant volume combustion
chamber (U.S. Pat. No. 6,206,940). However, laminar flame speeds or
burning velocities of fully blended fuels are not typically
measured, nor are they readily estimated through surrogate
analytical techniques. Whereas standardized octane measurements
have been carried out and consistent data acquired for a large
fraction of the hydrocarbons commonly found in commercial
gasolines, the same is not true for burning velocities, and
consequently the effects of fuel composition on burning velocity
are not well understood.
[0004] Several approaches have been investigated to boost the
burning velocity of a fuel. One approach is to add an additive not
normally present in commercial gasoline streams. For example, U.S.
Pat. No. 5,354,344 A1 describes a gasoline fuel composition
containing 5-50% by volume of the chemical 3-butyn-2-one. This
additive is said to improve the flame propagation speed, engine
output power, ignitability, and reduce cycle-to-cycle fluctuations,
although no assertions are made related to improving vehicle
efficiency. However, because this additive is a pure chemical
component that requires a multi-step chemical synthesis, its
introduction into commercial gasolines at the claimed dosages would
involve significant expense, and it is doubtful that the resulting
fuel could be made widely available.
[0005] U.S. Pat. No. 2,894,830 describes the use of small amounts
of boron hydrides in conventional fuels employed for heating or
propulsion purposes to increase the combustibility and the velocity
of flame propagation of such fuels.
[0006] WO 96/40844 A1 and WO 95/33022 A1 describe the introduction
of transition metals, alkaline metals, alkaline earths, halogens,
group IIIA elements and mixtures thereof into a fuel to increase
the fuel's combustion rate. U.S. Pat. No. 4,765,800 discloses that
alkali metal salts or alkaline metal earth salts of succinic acid
derivatives improve the ignitability of a mixture and shorten flame
travelling time. One serious drawback of these approaches is the
corresponding emission of uncommon and undesirable pollutants such
as boron compounds, metals, or halogens, which could foul
engine/exhaust aftertreatment systems and would likely require
complex aftertreatment controls to reduce environmental
contamination.
[0007] An approach to increase the laminar burning velocity of a
fuel that forgoes the use of additives is to modify its bulk
chemical composition. FIG. 1 shows data from four literature
sources that measured laminar burning velocities for a wide range
of molecules. The data are from Wagner and Dugger, JACS 77:227
1955, Gibbs and Calcote, J. Chem. Eng. Data, 4:226 1959, Albright,
Heath, and Thena, Industrial and Engineering Chemistry 44 10 1952,
pp. 2490-1496, and Gerstein, Levine, and Wong, J. Am. Chem. Soc.,
73:418 1951. As can be seen from the data, burning velocities are
available for only a small number of aromatics. Furthermore, the
data are contradictory. For example, Albright et al report
ethylbenzene to be the fastest aromatic while Wagner and Dugger
report benzene to be the fastest. The paucity of experimental
observations and uncertainties in the data render it difficult to
elucidate fuel structure effects from these studies. Thus, while
there is a general understanding in the art on how fuel structure
affects burning velocity for paraffins and olefins, no such
understanding exists for aromatics. The present invention resulted
from a thorough investigation of the burning velocity for a wide
range of aromatic components, from which we have found that the
fuel structure effects of aromatics are actually different from
that taught in the art. The resulting improved understanding makes
the optimization of burning velocity by tuning fuel composition
possible.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to an unleaded hydrocarbon
fuel such as a gasoline boiling range fuel comprising a paraffinic
fraction, an olefinic fraction, and an aromatics fraction having an
improved laminar burning velocity. The aromatics fraction comprises
methyl aromatics and non-methyl alkyl aromatics and the percentage
of non-methyl alkyl aromatics in the aromatics fraction is at least
30% on a volume basis. Preferably, the paraffinic fraction is in an
amount of 90% or less, the olefinic fraction is in an amount of 30%
or less, and the aromatics fraction is in an amount of 70% or less,
all calculated on a volume basis. Unless otherwise stated, all
percentages listed herein are on a volume basis. The term
"paraffinic" as used herein refers to normal, iso, and
cycloparaffins, and the term "olefinic" as used herein refers to
linear, branched, and cyclo-olefins. The components denoted
"non-methyl alkyl aromatics" include molecules such as
ethylbenzene, propylbenzene, butylbenzene, and the like, in which a
single alkyl chain containing two or more carbons is bonded to the
aromatic ring. The components denoted "methyl aromatics" include
aromatic molecules such as toluene, o, m, and p-xylenes,
trimethylbenzenes, methyl ethylbenzenes, and the like. Components
such as oxygenates, di-olefins, benzene, other aromatics and
naphthoaromatics may also be included in the hydrocarbon fuel.
[0009] The hydrocarbon fuel preferably contains benzene in an
amount less than 1% by volume and sulfur less than 30 ppm by
weight.
[0010] The invention is also directed to an unleaded hydrocarbon
fuel comprising a paraffinic fraction, an olefinic fraction, and an
aromatics fraction, wherein said methyl aromatics fraction
comprises xylenes (dimethyl benzenes) and the percentage of ortho-
and para- substituted xylenes is at least 60% on a volume
basis.
[0011] The invention further relates to a method for making a
hydrocarbon fuel such as unleaded gasoline, low sulfur gasoline,
and low benzene gasoline having an improved laminar burning
velocity. The terms laminar burning velocity and laminar flame
speed are often used interchangeably in the literature and this
practice will be followed herein.
[0012] The method comprises providing a hydrocarbon fuel having a
paraffinic fraction, an olefinic fraction, and an aromatic
fraction. The aromatic fraction may comprise methyl aromatics and
non-methyl alkyl aromatics. The method includes controlling the
concentration of the non-methyl alkyl aromatics in the aromatics
fraction to at least 30% by volume. Yet another aspect of the
invention is directed to controlling the percentage of ortho- and
para-xylenes in the xylene fraction to at least 60% by volume. The
paraffinic fraction may comprise normal (linear), branched (iso),
and cyclo-paraffins, the olefinic fraction may comprise linear,
branched, and cyclo-olefins.
[0013] The present inventive method and hydrocarbon fuel are
advantageous over conventional methods and fuels. Specifically,
inventive fuel compositions exhibit increased laminar burning
velocities and substantially improved engine thermal efficiencies.
A substantially improved thermal efficiency as this term is used in
this invention means a relative brake thermal engine efficiency of
at least 0.5%, preferably at least 1.5% and most preferably at
least 2% greater than the brake thermal efficiency obtained with an
unmodified conventional fuel. Likewise, a substantially improved
burning velocity as this term is used in this invention means a
burning velocity of at least 4%, preferably at least 10% and most
preferably at least 15% greater than the burning velocity of an
unmodified conventional fuel.
[0014] Another advantage of the inventive hydrocarbon fuel
composition is that higher burning velocities also improve lean
burn engine operation. Lean burn engines are generally known to
improve engine efficiency but conventional gasoline blends often
burn too slowly to allow a maximum benefit to be extracted. The
burning velocity benefits identified in the present invention apply
over substantially the entire fuel/air stoichiometry range, i.e.,
they are not limited to one operating regime such as
stoichiometric, lean, or rich operation. As such, they are useful
in extending the lean limit of engine operation thereby increasing
engine efficiency. Additionally, the faster heat release provided
by fast burning fuels maximizes the power and/or torque output of
the engine. A significant improvement of torque output enabled by a
fuel composition could allow engine downsizing and thus recover
additional efficiency benefits from reduced vehicle weight.
Additionally, the inventive compositions have the significant
advantage that they can be produced from refinery streams and thus
have the potential of being supplied in large quantities at low
cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows the peak burning velocities of several aromatic
hydrocarbon species as reported in Wagner and Dugger, JACS 77:227,
1955, Gibbs and Calcote, J. Chem. Eng. Data, 4:226 1959, Albright,
Heath, and Thena, Industrial and Engineering Chemistry, 44:2490
1952, and Gerstein, Levine, and Wong, J. Am. Chem. Soc., 73:418
1951.
[0016] FIG. 2 shows a schematic representation of a constant volume
combustion vessel used for laminar burning velocity determinations.
A) optical arrangement; B) simplified gas diagram.
[0017] FIG. 3 shows peak burning velocity data for several aromatic
hydrocarbon compounds in the gasoline boiling point range, acquired
at T=450K and P=3 atm.
[0018] FIG. 4 shows laminar burning velocity data at T=450 K and
P=3 atm for several aromatic species as a function of equivalence
ratio .phi..
[0019] FIG. 5 shows laminar burning velocity data at T=450 K and
P=3 atm for two fast fuel formulations compared to a reference
gasoline according to one embodiment of the present invention.
[0020] FIG. 6 shows the relative burning velocities at T=450 K and
P=3 atm for a fast and slow fuel blend according to one embodiment
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The laminar burning velocities of more than 30 hydrocarbons
were measured in a constant volume combustion vessel under
temperatures and pressures that approximate in-cylinder conditions.
The apparatus is shown schematically in FIG. 2. The measurements
were carried out in a stainless steel vessel with a 16.5 cm
diameter spherical cavity (volume=2.4 liter) with four windows for
optical access. The vessel was housed in a temperature-controlled
oven with quartz windows to transmit Schlieren and ignition laser
beams. Liquid fuels were pre-vaporized in an 11 liter stainless
steel vessel housed outside of the oven. The vaporized fuel mixture
was metered into the combustion vessel using a high sensitivity
pressure transducer (PT). Measurements were made over a very wide
range of equivalence ratios to characterize the burning velocity
dependence on stoichiometry. The symbol .phi. denotes the fuel/air
equivalence ratio, wherein a value of .phi.=1.0 represents a
stoichiometric fuel/air mixture. The air charge was admitted next
until the desired pressure was achieved. The mixtures were ignited
in the center of a spherical vessel with a laser pulse at an
initial temperature of 450 K and initial pressure of 3 atm. The
data were acquired over a stoichiometry range of a fuel to air
ratio (.PHI.) of from about 0.55 to about 1.30 to determine how the
fuel to air ratio affects the burning velocity. Following ignition,
the pressure rise in the vessel is monitored with a fast, high
dynamic range pressure transducer.
[0022] The data of pressure as a function of time data were
converted via a thermodynamic analysis to mass fraction burned
based on the established approach described by Metghalchi and Keck
[Metghalchi, M. and Keck, J. C.; "Burning velocities of mixtures of
air with methanol, isooctane, and indolene at high pressure and
temperature", Combustion and Flame, 1982, vol. 48, pp. 191-210].
Data from the pressure-based measurements are extrapolated back to
the initial conditions (450 K and 3 atm) to ensure that the fuels
are compared under the same temperature and pressure conditions.
This method utilizes data in which the flame radius is much greater
than the flame thickness, rendering the effects of stretch
negligible. The results for ethane and butane acquired under
ambient conditions (300 K and 1 atm), for which accurate literature
data are available for comparison, were obtained for the purpose of
validating the techniques used herein for accurately determining
burn velocity.
[0023] The results show that, of the fuels studied, methane is the
slowest paraffin and ethane the fastest. Generally, olefins have a
faster burning velocity than the corresponding paraffins. By
corresponding paraffin we mean a paraffin that has the same carbon
connectivity as a given olefin, e.g., iso-butene and iso-butane,
2,2,4 trimethyl pentane and 2,4,4-trimethyl-1-pentene, etc.
Branched paraffins are slower than non-branched (linear) paraffins,
and branched olefins are slower than non-branched (linear) olefins.
Aromatics other than benzene are generally slower than the olefins
and paraffins, while oxygenates are faster.
[0024] The burning velocities of aromatics are illustrated in FIG.
3. As shown, methyl benzenes such as the xylenes and
trimethylbenzenes are slower than the non-methyl alkyl aromatics
such as ethylbenzene and propylbenzene. Moreover, FIG. 3 shows that
among the multi-methyl aromatics such as the xylenes and trimethyl
benzenes, in which more than one methyl group is substituted on the
aromatic ring, the sites of methyl substitution influence burning
velocity, that is, ortho- and para-substituted isomers have a
higher burning velocity than the meta-substituted isomers.
[0025] One aspect of the present invention relates to a method for
blending a fuel such as gasoline to increase laminar burning
velocity. Such a blended fuel will yield benefits in any engine
(either spark ignition, compression ignition, or a combination
thereof) in which flame propagation is operative in consuming the
fuel. Generally the method includes controlling the composition of
the aromatic component of the fuel as taught herein. We have found
that the laminar burning velocity of a fuel increases with the
following general changes: a) increasing the concentration of
non-methyl alkyl aromatics and decreasing the concentration of
methyl aromatics, and b) increasing the concentration of ortho- and
para-substituted multi methyl aromatics.
[0026] One embodiment of the invention increases the laminar
burning velocity of a full-range gasoline by altering the
composition in such a way as to increase the concentration of
"preferable" compounds and decrease the concentration of "less
preferable" compounds, while keeping the overall percentage of
olefins, paraffins, and aromatics unchanged. The term "preferable
compounds" means compounds that, according to the teaching of this
invention, increase the fuel's burning velocity. For example, one
embodiment of the invention includes keeping the total
concentration of aromatics in the fuel constant while increasing
the ratio of non-methyl alkyl aromatics in the aromatic fraction,
such as ethylbenzene, n-propylbenzene, iso-propylbenzene, and
t-butylbenzene, and/or decreasing the methyl aromatics such as
toluene, xylene, and trimethylbenzenes. It has been discovered that
the variation in burning velocity between the fastest and slowest
aromatics in the gasoline boiling range is about 50%, which is
higher than the variations observed among olefins and paraffins in
this boiling point range.
[0027] Engine and vehicle data obtained indicate that these
modifications can translate into a substantial thermal efficiency
improvement of at least about 0.5%, preferably at least about 1.5%,
and more preferably at least about 2%. For example, according to
one embodiment of the invention two fuels with laminar burning
velocities that differ by 1% yield a 2% difference in the relative
brake thermal efficiency in an engine test.
[0028] Thus, according to the present invention, a fuel's burning
velocity can be increased by increasing the proportion of
non-methyl alkyl aromatics to methyl aromatics, and increasing the
proportion of ortho- and para-xylene to m-xylene.
[0029] As shown in FIG. 4, the relative ranking of the aromatics
persists to both lean and rich conditions, meaning that the
improvements in burning velocity achieved by varying the fuel
composition may be realized across the entire load-speed operating
map of the engine. Stated alternately, since there are no
discernible differences between the fuels as a function of fuel/air
ratio .phi., that is, the relative differences between the fuels
are effectively the same under lean, stoichiometric, and rich
conditions, there is no basis for defining preferential composition
for only a given part of the drive cycle based on flame speed
differences.
[0030] An embodiment of the present invention relates to a
hydrocarbon fuel comprising a paraffinic fraction in an amount of
90% or less, an olefinic fraction in an amount 30% or less, and an
aromatics fraction in an amount of 70% or less, wherein said
aromatics fraction comprises methyl aromatics and non-methyl alkyl
aromatics and the concentration of non-methyl alkyl aromatics in
said aromatics fraction is at least 30%. Preferably, the
concentration of non-methyl alkyl aromatics in the aromatics
fraction may be at least 50%, and more preferably at least 70%.
[0031] In another preferred embodiment, the methyl aromatics
fraction comprises xylenes and the percentage of ortho- and
para-xylene in said xylene fraction is at least 60%. Preferably,
the concentration of ortho- and para-xylene in said xylene fraction
may be at least 75%, and more preferably at least 90%.
[0032] The present invention also relates to a method for making a
hydrocarbon mixture in the gasoline boiling point range having an
improved laminar burning velocity. The method comprises providing a
gasoline comprising a paraffinic fraction, an olefinic fraction,
and an aromatic fraction. The paraffinic fraction comprises linear,
branched, and cyclo-paraffins, the olefinic fraction comprises
linear, branched, and cyclo-olefins, and the aromatic fraction
comprises methyl aromatics and non-methyl alkyl aromatics. The
method further comprises controlling the concentration of the
non-methyl alkyl aromatics in the aromatics fraction to at least
30% and the percentage of ortho- and para-substituted xylene in the
xylene fraction to 60%.
[0033] A preferred embodiment comprises controlling the percentage
of non-methyl alkyl aromatics in the aromatics fraction to at least
50% and the percentage of ortho- and para-substituted xylene in the
xylene fraction to 75%.
[0034] A most preferred embodiment comprises controlling the
percentage of non-methyl alkyl aromatics in the aromatics fraction
to at least 70% and the percentage of ortho- and para-substituted
xylene in the xylene fraction to 90%. These and other embodiments
of the invention will become more apparent to those skilled in this
art from the following examples.
[0035] It has been found that higher burning velocity correlates
with increased efficiency in vehicle tests. Data have been obtained
with a prototype vehicle (4-speed ATM, IW=1360 kg) with a
4-cylinder, direct injection gasoline engine. The vehicle was
evaluated with a U.S. driving cycle in which lean-burn operation
was achieved for half the drive cycle. Multiple test fuels, and a
base fuel were evaluated in which the aromatics level, olefin
level, and volatility were varied. Laminar burning velocity
measurements show that there was about an 11% variation in burning
velocity which resulted in about a 2% relative efficiency
difference in the vehicle.
EXAMPLE 1
[0036] Two model fuels were blended to have a RON and boiling point
distribution comparable to a conventional U.S. gasoline. The
molecular components were chosen on the basis of maximizing where
possible those molecules which have an elevated burning velocity.
The fuel composition (all values in weight %) and properties are
shown in Table 1.
1 TABLE 1 Fuel FF1 Fuel FF2 REF Gasoline 1-hexene 23.43 3.50
cyclohexane 9.10 methylcyclohexane 5.35 4.99 iso-octane 31.79
1-pentene 5.35 4.16 3-heptene 3.90 16.35 ethylbenzene 30.18 11.26
1.90 toluene 50.64 8.32 c6 isoparaffins 8.79 c7 isoparaffins 6.68
c9 aromatics 6.54 c5 isoparaffins 6.07 c5 olefins 5.37 c11
naphthenes 4.84 n-pentane 4.81 c8 olefins 4.55 n-hexane 4.17 c10
aromatics 4.03 c11 aromatics 3.23 c11 aromatics 3.23 m-xylene 3.13
c8 isoparaffins 2.37 c6 olefins 2.37 c4 olefins 2.11 butane 1.72 c7
olefins 1.50 o-xylene 1.47 n-heptane 1.46 p-xylene 1.13 n-octane
0.63 sum 100.0 100.0 90.4.sup.1 RON 92.1 92.8 89.8 .sup.1The large
number of remaining components are present at very small
concentrations (<1% each) and are not shown.
[0037] The burning velocity data for these fuels and a conventional
reference gasoline (REF gasoline) are shown in FIG. 5. It can be
seen that the molecular constituents can be preferentially chosen
to significantly enhance the burning velocity of the fuel.
EXAMPLE 2
[0038] Two fuel blends were prepared containing a single aromatic,
olefinic, and paraffinic component. Blend one was composed of
iso-octane, 2,4,4-trimethyl-1-pentene, and m-xylene, which are a
"slow" paraffin, olefin, and aromatic, respectively. Blend 2 was
composed of n-pentane, 1-hexene, and iso-propylbenzene, which are a
"fast" paraffin, olefin, and aromatic, respectively. The
concentrations of the paraffin, olefin, and aromatic were chosen to
approximate those in commercial gasoline. The compositions of these
fuels are shown in the table below.
2 TABLE 2 Aromatic Methyl/Non-Methyl Vol % Vol % Alkyl Component
Fuel 1 Fuel 2 Fuel 1 Fuel 2 n-pentane 60 iso-octane 60 1:0 1-hexene
10 2,4,4-trimethyl-1-pentene 10 0:1 isopropyl benzene 30 m-xylene
30 Total 100 100
[0039] The burning velocities of these fuels were determined at
450.degree. K and 3 atm. The results, shown in the FIG. 6, show
that a burning velocity increase of 17% was achieved solely by
replacing the "slow" paraffins, olefins, and aromatics with "fast"
analogues. Thus, preferentially tailoring the molecular structure
of paraffins, olefins, and aromatics, without changing the bulk
concentration of these constituents, increases burn rate, and by
extension, engine efficiency.
* * * * *