Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
LOW LEAD AVIATION GASOLINE BLEND
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a reduced or low lead aviation gasoline
blend which satisfies the requirements of ASTM D 910 or deviates therefrom
only in the
inclusion of an oxygenate. In particular the invention relates to such an
aviation gasoline
blend which comprises at least about 50 % by volume 2,2,4-trimethylpentane and
contains less than the maximum of 0.53 mL/L of lead specified by ASTM D 910.
The Prior Art Background
Tetraethyl lead (TEL) was used for years to increase octane in both
automotive and aviation gasoline fuels. On January 1, 1996 TEL was banned from
use
in automotive gasoline fuels by the EPA Clean Air Act. The General Aviation
industry
is concerned that these criteria will be extrapolated to aviation gasoline
fuels so as to
increase the cost and affect the reliability and/or consistency thereof. This
concern is
exacerbated because aviation gasoline fuel generally must have a higher octane
than
automotive fuel. Moreover, consumers in the general aviation industry require
a gasoline
fuel product which has a consistent and reliable octane rating so as to
provide an
appropriate consistent performance level.
Generally speaking, aviation gasoline fuels today must meet the
requirements of ASTM D 910 (1996). Presently relevant criteria of ASTM D 910
are
set forth below in TABLE 1.
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TABLE 1
D 5191 Vapor pressure 38.0-49.0 kPa
D 3338Heat of combustion, net 43.5 MJ/kg min
D 5059Lead content 0.53 mL/L max
D 2700Motor octane number (MON)
(BRE/30.2in/300F) 99.5 min
D 909 ASTM Supercharge rating
(1.31 mL TEL/gal)
Performance number 130.0 min
D 86 Distillation, C, % evaporated
10% 75 max
40% 75 min
50% 105 max
90% 135 max
Final boiling point 170 max
Sum of 10 % + 50 %
evaporated 135 min
Recovery 97 % min
Residue 1.5 % max
Loss 1.5 % max
ASTM D 910 also excludes oxygenates. To meet the criteria of ASTM
D 910, most aviation gasoline fuels today comprise a blend containing about 70
volume
% alkylate, about 10 volume % isopentane and about 20 volume % toluene.
Approximately 2 gm of TEL is added to each gallon of the blend to
appropriately increase
the MON to the specified level. This is the maximum amount of lead allowed by
the
ASTM D 910 specification. The very stringent specifications set by ASTM D 910
(1996)
for aviation gasoline fuels, particularly the supercharge octane rating, the
MON, the vapor
pressure and the distillation criteria greatly reduce the options available to
blend a
satisfactory aviation gasoline fuel without using a lead additive to increase
the octane
level. In fact most prior art aviation gasoline fuel blends have necessarily
included the
maximum amount of lead permitted.
The ASTM D 910 (1996) specification sets only a maximum level for
lead. Accordingly, aviation gasoline with no lead would be suitable assuming
all other
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criteria are met. At this point in time the EPA is adamant about reducing or
eliminating
lead in aviation gasoline and it is believed that the main reason that the EPA
has not yet
moved on this point is that there currently is no solution to the problem of
achieving high
enough octane in aviation gasoline fuels without using lead. Were the EPA to
move now,
it might lead to the destruction of the entire general aviation industry.
So a maj or unsolved problem in the general aviation industry today is how
to provide an aviation gasoline fuel which meets all of the criteria of the
ASTM D 910
(1996) specification without using lead as an additive. Stated another way,
the problem
is how to reduce or eliminate the need for lead in aviation gasoline fuels.
SUMMARY OF THE INVENTION
The present invention provides a genuine solution to the problems
discussed above. Thus, the invention provides a reduced lead aviation gasoline
blend
which satisfies the requirements of ASTM D 910. In particular, the invention
provides
an aviation gasoline fuel that comprises at least about 50.0 volume % 2,2,4-
trimethylpentane (sometimes referred to simply as "isooctane"), whereby the
lead content
of the fuel may be reduced to less than 0.53 mL/L. Thus, the fuel of the
invention may
comprise at least about 50.0 volume % 2,2,4-trimethylpentane, meets the
requirements
of ASTM D 910, and contains less than 0.53 mL/L lead.
More particularly, the invention provides a gasoline blend which is
suitable for use in an internal combustion airplane engine and which contains
no more
than 0.26 mL/L of lead and which may comprise from about 55.0 to about 65.0
volume
% of 2,2,4-trimethylpentane. Preferably the gasoline blend of the invention
may
comprise from about 58.0 to about 62.0 volume % of the 2,2,4-trimethylpentane.
More
preferably the gasoline blend of the invention may comprise about 60.0 volume
% of the
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2,2,4-trimethylpentane. Ideally, the gasoline blend of the invention may
comprise no
more than about 85.0 volume % of the 2,2,4-trimethylpentane.
Through the use of the invention, the lead content of the gasoline blend
may be reduced from the maximum allowed by ASTM D 910 to an amount which
ranges
from about 0.11 to about 0.15 mL/L. Preferably, and in accordance with one
aspect of
the invention, the lead content may range from about 0.12 to about 0.14 mL/L.
Ideally,
in accordance with this aspect of the invention, the lead content of the fuel
may be about
0.13 mL/L. In fact, the lead content of the aviation fuel may be reduced to an
amount
which is no more than about 0.13 mL/L.
Through the use of another aspect of the invention, wherein the gasoline
blend includes an oxygenate, the lead content of the gasoline blend may be
reduced from
the maximum allowed by ASTM D 910 to an amount which ranges from about 0.03 to
about 0.07 mL/L. Preferably, in accordance with this aspect of the invention,
the lead
content may range from about 0.04 to about 0.06 mL/L. Ideally, in accordance
with this
aspect of the invention, the lead content of the fuel may be about 0.05 mL/L.
In fact, the
lead content of the aviation fuel may be reduced to an amount which is no more
than
about 0.05 mL/L.
A predominant feature of the invention is the use of a major amount of
2,2,4-trimethylpentane in the gasoline blend. As mentioned above, the content
of this
ingredient in the overall gasoline blend may be as low as 50.0 % and as high
as 85.0 %
by volume. Preferably, the blend may contain about 60.0 volume % of the 2,2,4-
trimethylpentane. In accordance with another aspect of the invention the
gasoline blend
may contain about 67.0 volume % of said 2,2,4-trimethylpentane.
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The aviation gasoline blend of the invention may also include a C,-Cõ
aromatic hydrocarbon, a C5-C6 aliphatic hydrocarbon and a C4 aliphatic
hydrocarbon.
Preferably the blend may contain a sufficient amount of a C,-Cõ aromatic
hydrocarbon
to provide an appropriate supercharge rating. Furthermore, the blend may
include a
sufficient amount of a C5-C6 aliphatic hydrocarbon to provide D-86
distillation control.
Additionally, the blend may include a sufficient amount of a C4 aliphatic
hydrocarbon to
provide D-86 distillation and RVP control.
In one highly preferred embodiment ofthe invention, the aviation gasoline
blend may comprise from about 56.0 to about 64.0 volume % 2,2,4-
trimethylpentane,
from about 13.0 to about 17.0 volume % xylene, from about 12.0 to about 16.0
volume
% methyl t-butyl ether, from about 6.5 to about 9.5 volume % isopentane, from
about 2.0
to about 4.0 volume % isobutane and no more than about 0.1 mL/L tetraethyl
lead. More
preferably, the aviation gasoline blend of the invention may comprise from
about 58.0
to about 62.0 volume % 2,2,4-trimethylpentane, from about 14.0 to about 16.0
volume
% xylene, from about 13.0 to about 15.0 volume % methyl t-butyl ether, from
about 7.0
to about 9.0 volume % isopentane, from about 2.5 to about 3.5 volume %
isobutane and
no more than about 0.07 mL/L tetraethyl lead. Ideally the blend may include
about 60.0
volume % 2,2,4-trimethylpentane, about 15.0 volume % xylene, about 14.0 volume
%
methyl t-butyl ether, about 8.0 volume % isopentane, about 3.0 volume %
isobutane and
no more than about 0.05 mL/L tetraethyl lead.
In another highly preferred embodiment of the invention, the aviation
gasoline blend may comprise from about 62.0 to about 72.0 volume % 2,2,4-
trimethylpentane, from about 15.0 to about 21.0 volume % xylene, from about
10.0 to
about 14.0 volume % isopentane, from about 2.0 to about 4.0 volume % isobutane
and
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no more than about 0.20 mL/L tetraethyl lead. More preferably, the aviation
gasoline
blend of this embodiment may comprise from about 64.0 to about 70.0 volume %
2,2,4-
trimethylpentane, from about 16.0 to about 20.0 volume % xylene, from about
10.5 to
about 13.5 volume % isopentane, from about 2.5 to about 3.5 volume % isobutane
and
no more than about 0.20 mL/L tetraethyl lead. Ideally, the blend of this
embodiment may
include about 67.0 volume % 2,2,4-trimethylpentane, about 18.0 volume %
xylene, about
12.0 volume % isopentane, about 3.0 volume % isobutane and no more than about
0.13
mL/L tetraethyl lead.
In a broader sense, and in one preferred aspect of the invention, the
aviation gasoline blend of the invention may include from about 56.0 to about
64.0, more
preferably from about 58.0 to about 62.0 and ideally about 60.0 volume % 2,2,4-
trimethylpentane, from about 13.0 to about 17.0, more preferably from about
14.0 to
about 16.0 and ideally about 15.0 volume % of a C,-C11 aromatic hydrocarbon,
from
about 12.0 to about 16.0, more preferably from about 13.0 to about 15.0 and
ideally about
14.0 volume % of an oxygenate, from about 6.0 to about 10.0, more preferably
from
about 7.0 to about 9.0 and ideally about 8.0 volume % of a branched aliphatic
Cs-C6
hydrocarbon, from about 2.0 to about 4.0, more preferably from about 2.5 to
about 3.5
and ideally about 3.0 volume % of a branched C4 aliphatic hydrocarbon and no
more than
about 0.1 mL/L tetraethyl lead.
In another preferred aspect of the broader invention, the aviation gasoline
blend of the invention may include from about 63.0 to about 70.0, more
preferably from
about 65.0 to about 69.0 and ideally about 67.0 volume % 2,2,4-
trimethylpentane, from
about 15.0 to about 21.0, more preferably from about 16.5 to about 19.5 and
ideally about
17.0 volume % of a C,-C11 aromatic hydrocarbon, from about 10.0 to about 14.0,
more
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preferably from about 11 to about 13 and ideally about 12 volume % of a
branched
aliphatic C5-C6 hydrocarbon, from about 2.0 to about 4.0, more preferably from
about
2.5 to about 3.5 and ideally about 3.0 volume % of a branched C4 aliphatic
hydrocarbon and no more than about 0.2 mL/L tetraethyl lead.
In a larger, broader sense, the invention provides an aviation gasoline
blend which satisfies the requirements of ASTM D 910, contains no more than
0.26
mL/L of lead and comprises a sufficient amount of 2,2,4-trimethylpentane to
provide
the blend with a motor octane number of at least 99.5.
Accordingly, in one aspect of the present invention there is provided an
aviation gasoline blend which satisfies the requirements of ASTM D 910,
contains
less than 0.53 mL/L of lead and comprises at least about 50.0 volume % 2,2,4-
trimethylpentane.
According to another aspect of the present invention there is provided
an oxygenated aviation gasoline blend which deviates from the requirements of
ASTM D 910 only in that it includes an oxygenate, which contains less than
0.53
mL/L of lead and which comprises at least about 50.0 volume % 2,2,4-
trimethylpentane.
According to yet another aspect of the present invention there is
provided an oxygenated aviation gasoline blend which deviates from the
requirements
of ASTM D 910 only in the inclusion of an oxygenate, which contains no more
than
0.26 mL/L of lead and which comprises a sufficient amount of 2,2,4-
trimethylpentane
to provide said blend with a motor octane number of no less than 99.5.
According to an aspect of the present invention there is provided an aviation
gasoline blend which satisfies the requirements of ASTM D 910, contains less
than
0.53 mL/L of lead and comprises between 50 and 85% 2,2,4-trimethylpentane by
volume.
According to a further aspect of the present invention there is provided an
oxygenated aviation gasoline blend which deviates from the requirements of
ASTM D
910 only in that it includes an oxygenate, which contains less than 0.53 mL/L
of lead
and which comprises between 50 and 85% 2,2,4-trimethylpentane by volume.
According to a further aspect of the present invention there is provided an
aviation gasoline blend which satisfies the requirements of
ASTM D 910, which contains less than 0.26 mL/L of lead and which comprises
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between 50 and 85% 2,2,4-trimethylpentane by volume, said blend having a motor
octane number of no less than 99.5.
According to a further aspect of the present invention there is provided an
oxygenated aviation gasoline blend which deviates from the requirements of
ASTM D
910 only in the inclusion of an oxygenate, which contains no more than 0.26
mL/L, of
lead and which comprises between 50 and 85% 2,2,4-trimethylpentane by volume,
said blend having a motor octane number of no less than 99.5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention provides an aviation gasoline fuel blend which includes
a reduced amount of lead and still complies with all of the criteria set by
the ASTM D
910 specification for aviation fuel. These criteria of ASTM D 910 are set
forth above
in TABLE 1. In accordance with the invention, the principal component of the
aviation gasoline of the invention is 2,2,4-trimethylpentane, a C8 branched
chain
aliphatic hydrocarbon that is sometimes referred to as isooctane. Preferably
the
isooctane is present in the fuel of the invention in an amount which is at
least 50.0
volume % of the entire blend. Isooctane may be present in any amount up to and
including about 85.0 volume %. When isooctane is present in an amount less
than
about 50% by volume, the octane will generally be too low. When the amount of
isooctane exceeds 85.0%, the vapor pressure will be too low and the
distillation
profile will not meet the ASTM D 910 criteria.
As is well known to those of ordinary skill in the art which pertains to
the present invention, the blending of useful gasoline fuels, for either
automobile or
aviation use, is more an art than a science. Each component may provide a
specific
property or
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characteristic; however, when such a component is added to a blend it may tend
to alter
other necessary properties and characteristics. Accordingly, much trial and
error is
necessarily involved in order to achieve a blend which meets all of the
criteria which have
been preordained, such as, for example, by the ASTM D 910 specification. Thus,
when'
one adds a component such as isooctane for the purpose of achieving a higher
octane, the
overall result may be that the vapor pressure becomes too low for the blend to
be useful.
Although prior workers in the field have tried alkylates which contain a
substantial isooctane portion, none have previously been successful. For
example, SAE
Technical Paper No. 971490 of J. N. Valentine et al., entitled "Developing a
High Octane
Unleaded Aviation Gasoline," presented during the General, Corporate &
Regional
Aviation Meeting & Exposition held at Wichita, Kansas on April 29 through May
1,
1999, describes certain experimental activities involving the testing of
blends containing
"a wide boiling range alkylate" in combination with an "octane boosting"
component
such as methyl-tertiary-butyl ether (MTBE) or ethyl-tertiary-butyl ether
(ETBE). The
wide boiling range allcylate included isooctane but the proportion thereof in
the alkylate
is not discussed. The final conclusion set forth by the authors was that "the
experimental
fuels blended for this program are not ready to be used in aircraft."
In accordance with one aspect of the present invention, the low lead
aviation gasoline fuel blends provided thereby comply fully with all of the
requirements
of ASTM D 910. In accordance with another aspect of the invention, the low
lead
gasoline fuel blends incorporate an oxygenate, but otherwise comply fully with
all of the
requirements of ASTM D 910. In both cases these blends are ready to be used in
aircraft.
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In addition to the isooctane, the aviation gasoline blends of the invention
preferably may include an aromatic component to increase supercharge rating
and one or
more lighter aliphatic hydrocarbons for distillation profile and RVP (Reid
Vapor
Pressure) control. The aromatic component may be a C7-Cõ aromatic hydrocarbon
and
preferably may be xylene or toluene. The aliphatic hydrocarbon components
ideally may
be branched compounds and preferably may have 4 to 7 carbon atoms in their
chains.
Preferably the aliphatic hydrocarbon components may include a mixture of
isopentane
and isobutane. The isopentane primarily is useful for controlling the
distillation profile
while the isobutane is useful for adjusting both distillation profile and
vapor pressure.
EXAMPLE I
A particularly useful aviation gasoline fuel blend which embodies the
principles and concepts of the present invention is as follows:
Isooctane (ASTM, Lot T-1304) 67.0 volume %
Xylene (Exxon LSC34893, 9902/973 88) 18.0 volume %
Isopentane (SHRCO, 9811/96252) 12.0 volume %
Isobutane (Instrument Grade, 99.5 % min.) 3.0 volume %
A 1.5 liter batch of the foregoing was prepared and TEL was added to provide a
final
concentration of 0.47 mL/gal. The chemical and physical characteristics of the
blend
were tested and the results are set forth in TABLE 2.
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TABLE 2
D 5191 Vapor pressure 48.6 kPa
D 3338 Heat of combustion, net 43.551 MJ/kg
D 5059 Lead content 0.13 mL/L
D 2700 Motor octane number (MON)
(BRE/30.2in/300F) 101.8
D 86 Distillation, C, % evaporated
10% 70
40% 102
50% 103.5
90% 124.5
Final boiling point 151.5
Sumof10%+50%
evaporated 173.5
Recovery 98.5%
Residue 0.5 %
Loss 1.0%
A second three gallon blend of essentially the same composition, except that
in this case
the blend contained 0.5 mL/gal of TEL, was tested in accordance with ASTM D
909 and
it was determined that the ASTM Supercharge rating (1.31 mL TEL/gal)
performance
number was 130.1.
As can be seen, the gasoline blend of EXAMPLE I complied fully with
the criteria set forth in ASTM D 910. Moreover, it can be seen that the lead
content of
0.13 mL/L is well below the specified maximum concentration of 0.53 mL/L. In
fact, the
lead concentration in the fuel of EXAMPLE I is only about 25 % of the
concentration
allowed by the ASTM D 910 specification. Thus, the fuel of EXAMPLE I provides
a 75
% reduction in the lead concentration when compared with the amount allowed by
ASTM
D 910.
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EXAMPLE II
Another highly useful aviation gasoline fuel blend which embodies the
principles and concepts of the present invention is as follows:
Isooctane (ASTM, Lot T-1304) 60.0 volume %
Xylene (Exxon LSC34893, 9902/973 88) 15.0 volume %
Methyl t-butyl ether
(Fisher Lot 980052, 99.9 %) 14.0 volume %
Isopentane (SHRCO, 9811/96252) 8.0 volume %
Isobutane (Instrument Grade, 99.5 % min.) 3.0 volume %
A batch of the foregoing was prepared and TEL was added to provide a final
concentration of 0.2 mL/gal. The chemical and physical characteristics ofthe
blend were
tested and the results are set forth in TABLE 3.
TABLE 3
D 5191 Vapor pressure 48.3 kPa
D 909 ASTM Supercharge rating
(1.31 mL TEL/gal)
Performance number 130.4
D 3338 Heat of combustion, net 43.581 MJ/lcg
D 5059 Lead content 0.05 mL/L
D 2700 Motor octane number (MON)
(BRE/30.2in/300F) 100.9
D 86 Distillation, C, % evaporated
10% 66.5
40% 94.5
50% 99.5
90% 119.5
Final boiling point 150.0
Sumof10%+50%
evaporated 166.0
Recovery 98.5 %
Residue 0.7 %
Loss 0.8 %
As can be seen, the gasoline blend of EXAMPLE II also complies fully
with the criteria set forth in ASTM D 910 except for the fact that it includes
an
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oxygenate. Moreover, it can be seen that the lead content of 0.05 mL/L is well
below the
specified maximum concentration of 0.53 mL/L. In fact, the lead concentration
in the
fuel of EXAMPLE II is only about 10 % of the maximum lead concentration
allowed by
the ASTM D 910 specification. Thus, the fuel of EXAMPLE II provides a 90 %
reduction in the lead concentration when compared with the amount allowed by
ASTM
D 910.
A purified isooctane for use in blending the aviation gasoline of the
invention may preferably be obtained by fractionation and hydrogenation of
crude
diisobutylene (DIB). Crude DIB having chemical and physical characteristics as
set forth
in TABLE 4 may be used as a starting material.
TABLE 4
D 5191 Vapor pressure, DVPE (40 CFR 80) 1.78 psi
D 358 Solubility in water, 25 C. 63 vol ppm
D 2699 Research octane number (RON)
(BRE/30.1 in/127F) 103.1
D 2700 Motor octane number (MON)
(BRE/30.1 in/300F) 86.0
D 5134 Hydrocarbon components Mass %
2,4,4-trimethyl-l-pentene 70.46
2,4,4-trimethyl-2-pentene 19.42
4,4-dimethyl-2-neo-pentyl-l-pentene 3.14
2,2,4,6,6-pentamethyl-3-heptene 3.65
Other diisobutylene isomers 0.47
Other triisobutylene isomers 2.81
Unidentified 0.05
D 86 Distillation, F, % evaporated
IBP 212 70% 224
5% 214 80% 230
10% 214 90% 261
20% 215 95% 346
30% 216 End 380
40% 217 Recovery 99.0%
50 % 219 Residue 1.0 %
60 % 222 Loss 0.0 %
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The crude DIB from TABLE 4 may be subjected to conventional
fractionation so as to obtain a finished DIB having chemical and physical
characteristics
as set forth in TABLE 5.
TABLE 5
D 5191 Vapor pressure, DVPE (40 CFR 80) 1.85 psi
D 358 Solubility in water, 25 C. 45 vol ppm
D 5134 Hydrocarbon components Mass %
2,4,4-trimethyl-l-pentene 79.55
2,4,4-trimethyl-2-pentene 19.87
Other diisobutylene isomers 0.33
Unidentified 0.25
D 86 Distillation, F, % evaporated
IBP 211
5% 212 80% 213
10% 212 90% 213
20% 212 95% 213
30% 212 End 237
40% 213
50% 213 Recovery 99.0%
60% 213 Residue 0.6%
70% 213 Loss 0.4%
The finished DIB of TABLE 5 may be subjected to conventional
hydrogenation processing so as to obtain a purified isooctane product
containing a very
high concentration of isooctane and having the physical and chemical
characteristics as
shown in TABLE 6.
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TABLE 6
D 5191 Vapor pressure, DVPE (40 CFR 80) 2.14 psi
D 358 Solubility in water, 25 C. 48 vol ppm
D 5134 Hydrocarbon components Mass %
2-methylhexane 0.02
2,2,4-trimethylpentane 99.54
1, 1,3 -trimethylcyclopentane 0.06
2,2,3-trimethylpentane 0.07
2,3,4-trimethylpentane 0.22
Toluene 0.01
2-methylheptane 0.03
n-octane 0.02
2,2,5-trimethylhexane 0.03
D 86 Distillation, F, % evaporated
IBP 205
5 % 207 80 % 208
10 % 207 90 % 208
% 207 95 % 209
30% 207 End 231
20 40 l0 207
50% 208 Recovery 99.0%
60% 208 Residue 0.6%
70 % 208 Loss 0.4 %
An objective of the processing described above is to provide a purified
isooctane material which may have a D 86 Distillation end point no greater
than about
337 F., preferably no greater than about 320 F., more preferably no greater
than about
250 F., and which even more preferably may be as low as 230 F. The clear
effort here
is to obtain an isooctane material having a D 86 Distillation end point which
approaches,
as nearly as possible, the atmospheric boiling point of pure isooctane. A
major limiting
factor may siinply be the cost of producing the purified isooctane material.
Suffice it to
say, the purer the better from a strict performance viewpoint; however, to
keep overall
costs low for commercial purposes, a purity of at least about 95 weight % may
be useful
in accordance with the invention to provide an appropriate D 86 Distillation
end point.
A purified isooctane material is desirable in accordance with the principles
and concepts
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of the invention so that the properties of an aviation gasoline prepared
therefrom are more
easily controlled.
It should be noted that the process steps described above could be
reversed. That is to say, the crude DIB of TABLE 4 could first be hydrogenated
to
produce a crude isooctane containing product blend having the physical and
chemical
characteristics described in TABLE 7.
TABLE 7
D 5191 Vapor pressure, DVPE (40 CFR 80) 1.94 psi
D 3120 Sulfur content <1 ppm
D 358 Solubility in water, 25 C. 46 vol ppm
D 2699 Research octane number (RON)
(BRE/30.5in/133F) 100.5
D 2700 Motor octane number (MON)
(BRE/30.5in/300F) 99.4
D 5134 Hydrocarbon components Mass %
2,2,4-trimethylpentane 87.67
Methylcyclohexane 0.58
Ethylcyclohexane 0.04
2,2,3-trimethylpentane 0.16
1 -trans-2-cis-4-trimethylcyclopentane 0.06
2,3-dimethylhexane 0.38
cis-1, 3 -dimethylcyclohexane 0.03
n-nonane 0.09
2,2,4,6,6-pentamethylheptane 7.23
Other C12 paraffins 3.76
D 86 Distillation, F, % evaporated
IBP 207
5 % 209 80 % 226
10% 209 90% 262
20 % 210 95 % 347
30% 211 End 389
40% 213
50% 214 Recovery 98.6%
60% 216 Residue 1.3%
70% 219 Loss 0.1%
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The crude isooctane blend of TABLE 7 may be fractionated using
conventional techniques to produce a purified isooctane blend which is
essentially the
same as the purified isooctane blend described above in TABLE 6.
No matter how it is produced, a purified isooctane material as described
in TABLE 6 is a supurb isooctane material for use in connection with the
present
invention. This material may be blended with the other ingredients discussed
above to
provide an excellent low lead aviation gasoline. The high purity of the
isooctane
facilitates control of the properties of an aviation gasoline prepared
therefrom. Thus, the
purified isooctane material of TABLE 6 may be used to prepare either the fuel
of
EXAMPLE I or the fuel of EXAMPLE II.
