Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MOTOR FUELS OF ENHANCED PROPERTIES
This invention relates to gasoline fuel compositions having superior
environmental and performance properties.
As is known, light ends of gasoline tend to evaporate into the atmosphere,
especially during warm or hot weather; but removal of the light ends to reduce
atmospheric pollution reduces the octane quality of the gasoline. Increased
proportions of aromatic gasoline hydrocarbons of high octane quality, such as
benzene, toluene, and xylene, can be used to compensate for this reduction in
octane
quality. However, since aromatics are not particularly desirable from the
toxicological standpoint; it would be desirable to provide a way of reducing
the front
end volatility of gasoline without having to increase the aromatics content.
The gasoline fuel composition of this invention has a Reid vapor pressure
(ASTM test method D-323) of 8.5 psi (58.6 kPa) or less, preferably 8.0 psi
(55:2 kPa)
or less, and contains up to 1/32 gram of manganese per gallon (0.008g/liter)
as at
least one fuel-soluble cyclopentadienyl manganese tricarbonyl compound. The
use
of cyclopentadienyl manganese tricarbonyls increases the octane quality of the
low
Reid vapor pressure gasoline without increasing its volatility and without
requiring
an increase in its aromatics content, and it has been found that these
manganese
compounds tend to exert a greater octane-improving effect in paraffinic and
naphthenic hydrocarbons than they do in aromatic gasoline hydrocarbons.
Moreover,
the use of the fuels of the invention results in reduced emission of carbon
dioxide
and nitrogen oxides (NOx) during engine operation while having little effect
on the
level of tailpipe hydrocarbon emissions; and they exhibit virtually no adverse
effect
upon exhaust gas catalysts and oxygen sensors of the type commonly used in
present-
day vehicles. Thus, the fuels of the invention are "environmentally friendly."
Other embodiments of the invention are improvements in (1) the normal
process for preparing a gasoline by blending together appropriate proportions
of
suitable hydrocarbons of the gasoline boiling range [typically 70-440 °
F (21.1-
226.7 ° C)] and/or (2) processes for distributing gasoline and/or
dispensing it to motor
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vehicles.
In the improved preparation of the gasoline; the aforementioned
cyclopentadienyl manganese tricarbonyl and low Reid vapor pressure fuel are
blended in any suitable manner, e.g., by (a) blending the fuel-soluble
additive into
the gasoline during or after completion of the gasoline blending procedures or
(b)
mixing the additive with one or more streams of gasoline hydrocarbons or other
blending components, such as oxygenated fuel blending components, before the
streams are blended together. The octane-enriched gasoline thus obtained may
then
be stored in at least one storage tank in a tank farm, if desired, before
being
distributed for use in fueling motor vehicles; and it may then be dispensed to
motor
vehicles.
These improved processes lessen the amount of volatile hydrocarbons released
into the atmosphere during storage and/or during fueling of a motor vehicle;
and,
in comparison with processes which utilize corresponding fuels containing no
cyclopentadienyl manganese tricarbonyl, they reduce the amount of carbon
monoxide
and nitrogen oxides released into the atmosphere during operation of motor
vehicles.
As noted above, the unleaded gasolines utilized in the practice of this
invention must have a Reid vapor pressure of 8.5 psi (58.6 kPa) or below, and
preferably 8.0 psi (55.2 kPa) or below. As is well known, Reid vapor pressures
are
determined at 100 ° F (37:8 ° C). Such gasolines are lead-free
in the sense that no
organolead antiknock agent is blended into the fuel, although they may contain
trace
amounts of lead contaminants. The hydrocarbonaceous gasoline base stocks that
are
used in forming the gasoline blends include straight run stocks, light naphtha
fractions, cracked gasoline stocks obtained from thermal or catalytic
cracking,
hydrocracking, or similar methods, reformate obtained by catalytic reformation
or
like processes, polymer gasolines formed via polymerization of olefins,
alkylates
obtained by addition of olefins to isobutane or other hydrocarbons by
alkylation
processes, isomerates formed by isomerization of lower straight chain
paraffins such
as n-hexane, n-heptane, and the like; and other hydrocarbons of the gasoline
boiling
range formed by suitable refinery processing operations. Suitable amounts of
appropriate hydrocarbons formed by other methods such as production from coal
or
_3_ 4 4
shale can be included, if desired. For example reformates based on liquid
fuels
formed by the Fischer-Tropsch process can be included in the blends. In all
cases,
the resultant gasoline must satisfy the Reid vapor pressure requirements of
this
invention and additionally will possess the distillation characteristics
typical of
S conventional regular, midgrade, premium, or super-premium unleaded
gasolines.
Thus the motor gasolines are generally within the parameters of ASTM D 4814
and
typically have initial boiling points in the range of 70-I1S ° F (21.1-
46.1 ° C) and final
boiling points in the range of 370-440 ° F (187.8-226.7 ° C) as
measured by the
standard ASTM distillation procedure (ASTM D 86). The hydrocarbon composition
of gasolines according to volume percentages of saturates, olefins, and
aromatics is
typically determined by ASTM test procedure D 1319.
Generally, the base gasoline will be a blend of stocks obtained from several
refinery processes. The final blend may also contain hydrocarbons made by
other
procedures such as alkylates made by the reaction of C4 olefins and butanes
using an
1S acid catalyst such as sulfuric acid or hydrofluoric acid, and aromatics
made from a
reformer.
The saturated gasoline components comprise paraffins and naphthenates.
These saturates are generally obtained from: (1) virgin gasoline by
distillation
(straight run gasoline), (2) alkylation processes (alkylates), and (3)
isomerization
procedures (conversion of normal paraffins to branched chain paraffins of
greater
octane quality). Saturated gasoline components also occur in so-called natural
gasolines. In addition to the foregoing, thermally cracked stocks,
catalytically cracked
stocks and catalytic reformates contain some quantities of saturated
components.
Olefinic gasoline components are usually formed by use of such procedures
2S as thermal cracking, and catalytic cracking. Dehydrogenation of paraffins
to olefins
can supplement the gaseous olefins occurring in the refinery to produce feed
material
for either polymerization or alkylation processes.
The gasoline base stock blends with which the cyclopentadienyl manganese
tricarbonyl additive is blended pursuant to this invention will generally
contain 40 to 80
volume % of saturates, 1 to 30 volume % olefins, and up to about 45 volume %
aromatics. Preferred gasoline base stock blends for use in the practice
Bt
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of this invention are those containing no more than 40% by volume of
aromatics,
more preferably no more than 30% by volume of aromatics, still more preferably
no
more than 28% by volume of aromatics, and most preferably no more than 25% by
volume of aromatics: Preferably, the overall fuel blend will contain no more
than
1% by volume and most preferably no more than 0.8% by volume of benzene.
Particularly preferred unleaded gasolines produced and/or utilized in the
practice of this invention not only meet the Reid vapor pressure criteria set
forth
hereinabove but in addition, are characterized by having (1) a maximum sulfur
content of 300 ppm, (2) a maximum bromine number of 20, (3) a maximum aromatic
content of 20% by volume; (4) a maximum content of benzene of 1% by volume,
and
(5) a minimum content of contained oxygen of 1% by weight in the form of at
least
one monoether or polyether, such gasoline having dissolved therein up to 1/32
gram
of manganese per gallon (3.8 liters) as methylcyclopentadienyl manganese
tricarbonyl.
Gasolines of this type not containing the manganese additive are sometimes
referred
to as reformulated gasolines. See for example Oil & Gas Journal, April 9,
1990,
pages 43-48.
From the standpoint of octane quality, the preferred gasoline base stock
blends are those having an octane rating of (R + M)/2 ranging from 78-95.
Any of a variety of cyclopentadienyl manganese tricarbonyl compounds, e.g.,
those of U.S. Pat. No. 2,818,417, can be used in the practice of this
invention.
Illustrative examples of these manganese compounds include the
cyclopentadienyl,
methylcyclopentadienyl, dimethylcyclopentadienyl, trimethylcyclopentadienyl,
tetra-
methylcyclopentadienyl, pentamethylcyclopentadienyl, ethylcyclopentadienyl,
diethyl-
cyclopentadienyl, propylcyclopentadienyl, isopropylcyclopentadienyl, tert-
butylcyclo-
pentadienyl, octylcyclopentadienyl, dodecylcyclopentadienyl,
ethylmethylcyclopenta-
dienyl, and indenyl manganese tricarbonyls, and mixtures of two or more such
compounds. Generally speaking, the preferred compounds or mixtures of
compounds
are those which are in the liquid state of aggregation at ordinary ambient
tempera-
tures, such as methylcyclopentadienyl manganese tricarbonyl,
ethylcyclopentadienyl
manganese tricarbonyl, liquid mixtures of cyclopentadienyl manganese
tricarbonyl and
methylcyclopentadienyl manganese tricarbonyl, and mixtures of methylcyclopenta-
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dienyl manganese tricarbonyl and ethylcyclopentadienyl manganese tricarbonyl.
The
most preferred compound because of its commercial availability and its
excellent
combination of properties and effectiveness is methylcyclopentadienyl
manganese
tricarbonyl.
The practice of this invention and various embodiments thereof is illustrated
by the following examples wherein the percentages of gasoline hydrocarbons are
by
volume. These examples are not intended to limit, and should not be construed
as
limiting, this invention.
EXAMPLE 1
An unleaded motor gasoline blend is produced containing 58.9% saturated
hydrocarbons, 17.5%' olefinic hydrocarbons and 23.6% aromatic hydrocarbons,
all of
the gasoline boiling range. The Reid vapor pressure of the blend is 8.5 psi
(58.6
,.
kPa). With this base fuel are blended methylcyclopentadienyl manganese
tricarbonyl
to a concentration of 1/32 gram of manganese per gallon (0.008 g/liter) and 4-
methyl-2,6-di-tert-butylphenol to a concentration of 7.5 pounds per thousand
barrels
(21.4 g/m3). After storing the motor gasoline over water in a field storage
tank on
a tank farm, the product is transported by tank trucks to gasoline filling
stations
where it is dispensed on demand to motor vehicles. The vehicles consume the
same
during their operation.
EXAMPLE 2
An unleaded motor gasoline of this invention is produced to contain 56.9
saturates, 20.0% olefins and 23.1% aromatics, all of the gasoline boiling
range. The
components are selected such that the Reid vapor pressure of the blend is 8.4
psi
(57.9 kPa). A mixture of tertiary butylated phenolic antioxidants containing
85% by
weight of 2,6-di-tert-butylphenol is blended into the fuel to a concentration
of 6.5
pounds per thousand barrels (18.5 g/m3). Methylcyclopentadienyl manganese
tricar-
bonyl is blended into the resultant blend to a concentration of 1/32 gram of
manganese per gallon (0.008 g/liter). This fuel is stored, transported, and
dispensed
to and utilized in the operation of motor vehicles, the majority of which
contain
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catalytic converters.
EXAMPLE 3
Into an unleaded motor gasoline (67.7% saturates, 7.5% olefins, 24.8%
aromatics) having a Reid vapor pressure of 8.0 are blended
methylcyclopentadienyl
manganese tricarbonyl and methyl tert-butyl ether in amounts such that the
resultant
fuel contains 1/32 gram of manganese per gallon (0.008 g/liter) and 2.7% by
weight
of oxygen as methyl tert-butyl ether. The finished fuel, which can contain,
and
preferably does contain, conventional amounts of antioxidant, metal
deactivator, and
carburetor detergent, is dispensed to and utilized in the operation of motor
vehicles
including passenger cars, buses, trucks, vans, and motorcycles.
EXAMPLE 4
Examples 1-3 are repeated except that in one case the respective motor fuels
contain 1/40 gram of manganese per gallon (0.007 g/liter), in another the
respective
motor fuels contain 1/50 gram of manganese per gallon (0.005 g/liter), in a
third
case, 1/64 gram of manganese per gallon (0.004 g/liter) and in still another
case,
1/100 gram of manganese per gallon (0.003 g/liter).
EXAMPLE 5
Examples 1-4 are repeated except that in each case the methylcyclopenta-
dienyl manganese tricarbonyl is replaced by an equal concentration of
manganese as
cyclopentadienyl manganese tricarbonyl.
EXAMPLE 6
Examples 1-4 are repeated except that in one series of cases the respective
fuels contain instead of methylcyclopentadienyl manganese tricarbonyl, a
mixture of
90% by weight of methylcyclopentadienyl manganese tricarbonyl and 10% by
weight
of cyclopentadienyl manganese tricarbonyl in amounts such that the respective
fuels
contain the same respective concentrations of manganese as the fuels of
Examples
1-4. In another series of cases, the respective fuels of Examples 1-4 contain
the same
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respective concentrations of manganese in the form of dimethylcyclopentadienyl
manganese tricarbonyl in lieu of the methylcyclopentadienyl manganese
tricarbonyl.
And in still another series of cases the specified concentrations of manganese
in the
fuels of Examples 1-4 are supplied by tert-butylcyclopentadienyl manganese
tricar-
S bonyl. In yet another series of cases the manganese additive used in forming
the
motor fuel compositions is indenylmanganese tricarbonyl instead of
methylcyclopenta-
dienyl manganese tricarbonyl.
EXAMPLE 7
With an unleaded gasoline formulated to contain 40.1% saturates, 15.3%
olefins, and 44.6% aromatics and having a Reid vapor pressure of 8.3 psi (57.2
kPa)
are blended the following components:
5 pounds per thousand barrels (14.3 g/m3) of a phenolic mixture composed
of 75% 2,6-di-tert-butylphenol, 10-15% 2-tert-butylphenol and 10-15% of
2,4,6-tri-tert-
butylphenol; and
1 pound per thousand barrels (2.9 g/m3) of N,N'-disalicylidene-
1,2-propanediamine.
Thereafter, methylcyclopentadienyl manganese tricarbonyl is blended into the
gasoline to a concentration equivalent to 1/32 gram of manganese per gallon
(0.008
g/liter).
EXAMPLE 8
An unleaded motor gasoline blend having a Reid vapor pressure of 7.8 psi
(53.8 kPa) is formulated from 72.5% saturates, 4.0% olefins, and 23.5%
aromatics
(of which less than 3% by volume is benzene so that the fuel contains less
than 1%
by volume of benzene). Methyl tert-butyl ether is blended into the base
gasoline in
amount sufficient to provide an oxygen content of 2.0% by weight in the fuel.
Thereafter methylcyclopentadienyl manganese tricarbonyl is blended into the
resultant motor fuel in an amount equivalent.to 1/35 gram of manganese per
gallon
(0.008 g/liter).
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EXAMPLE 9
Example 8 is repeated with the exceptions that (a) the initial gasoline blend
has a Reid vapor pressure of 7:9 psi (54.5 kPa) and is composed of 75.7%
saturates,
4.8% olefins, and 19.5% aromatics (of which aromatics, less than 3.5% by
volume is
benzene); and (b) a mixture of methyl tert-butyl ether and ethyl tert-butyl
ether is
blended into the fuel in an amount such that the content of the oxygenated
fuel
blend is equivalent to 2.5% by weight of oxygen.
EXAMPLE 10
Example 8 is again repeated except that (a) the initial gasoline blend has a
Reid vapor pressure of 7.7 psi (53.1 kPa) and is composed of 78.6% saturates,
4.4%
olefins and 17.0% aromatics (the entire fuel blend again containing less than
1% by
volume of benzene); and (b) in lieu of methyl tent-butyl ether, tert-amyl
methyl ether
is blended into the gasoline in an amount equivalent to an oxygen content in
the fuel
of 2.7% by weight.
EXAMPLE 11
Blended with the respective fuels of Examples 7-10 at a concentration level
of 100 pounds per thousand barrels, (285.3 g/m3) is a polyether amine deposit
control additive available commercially from Oronite Chemical Co. as OGA-480.
EXAMPLE 12
2;0 Blended with the respective fuels of Examples 7-10 at a concentration of
100
pounds per thousand barrels (285.3 g/rn3) is a polyalkenyl succinimide deposit
control
additive available commercially from Ethyl Petroleum Additives, Ltd. as HITEC
4450 additive.
EXAM PLE 13
Blended with the respective fuels of Example 7-10 at a concentration level of
100 pounds per thousand barrels (285.3 g/m3) is a polyisobutenyl amine deposit
control additive available commercially from Oronite Chemical Co. as OGA-472.
*Trade-mark
A
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As can be appreciated from the above examples, the fuels of this invention
can, and preferably do, contain additives in addition to the cyclopentadienyl
manganese tricarbonyl compound or compounds. Such other additives include
antioxidants, deposit-control additives (also known as induction system
cleanliness
additives or fuel detergents), and oxygenated materials such as dialkyl
ethers, all with
the proviso that the volatility of such materials does not cause the fuel to
exceed the
Reid vapor pressure limitations required pursuant to this invention. Other
additives
that may be employed include supplemental antiknock additives such as aromatic
amine antiknocks such as N-methyl aniline; iron antiknock compounds such as
ferrocene, methylferrocene, and butadiene iron tricarbonyl; and nickel
antiknock
compounds such as cyclopentadienyl nickel nitrosyl. Corrosion inhibitors,
metal
deactivators, demulsifiers, and dyes comprise other types of additives that
can be
employed.
Preferred oxygenated materials that can be, and preferably are, blended into
the fuels of this invention are ethers of suitable low volatility such as
methyl
tert-butyl ether, ethyl tert-butyl ether, tert-amyl methyl ether, and 2,2-
diethyl-1,3-pro-
panediol. Also useful are fuel-soluble esters and alcohols of suitably low
volatility
such as tent-butyl acetate, 1-hexanol, 2-hexanol, 3-hexanol, and
polyethoxyethanols.
Usually such oxygenated compounds are employed in amounts sufficient to
provide
up to 3 to 4 weight % oxygen in the fuel, provided such usage is consistent
with
existing or proposed legislation. Other suitable oxygen-containing blending
agents
include p-cresol, 2,4-xylene, 3-methoxyphenol, 2-methylfuran, cyclopentanone,
isovaleraldehyde, 2,4-pentanedione and similar oxygen-containing substances.
Preferred antioxidants for the fuels of this invention are hindered phenolic
antioxidants, such as 2,6-di-tert-butyl-phenol, 2,4-dimethyl-6-tert-
butylphenol,
4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-butyl-2,6
di-tert-butylphenol, and mixtures of tertiary butylated phenols predominating
in
2,6-di-tert-butylphenol. In some cases aromatic amine antioxidants can prove
useful
either alone or in combination with a phenolic, antioxidant. Antioxidants are
usually
employed in amounts of up to 25 pounds per thousand barrels (71.3 g/m3), the
amount used in any given case being dependent upon the stability (e.g., olefin
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content) of the gasoline.
Another type of additives preferably utilized in the fuels of this invention
are
ashless detergents such as polyether amines, polyalkenyl amines, alkenyl
succinimides,
polyether amide amines, and the like. Such materials can be used at treat
levels of
50 to 500 pounds per thousand barrels (142.6-1426.4 g/m3), and more usually in
the
range of 100 to 200 pounds per thousand barrels (285.3-570.6 g/m3).
The cyclopentadienyl manganese tricarbonyl compounds as well as the other
supplemental additives or blending agents can be blended with the base fuels
according to well known procedures utilizing conventional mixing equipment.
This
invention is directed to all such fuel compositions meeting the primary
requisites of
this invention.
Driving tests were conducted on a 48-car fleet for a total of more than three
million test miles (4.8 x 106 km). Half of the cars of each model group were
run on
"clear" (i.e.; manganese additive-free) test fuel. The other half were run on
the same
fuel containing 1/32 of a gram of manganese per gallon (0.008 g/liter) as
methyl-
cyclopentadienyl manganese tricarbonyl. The inspection data on the base fuel
are
set forth in the following table.
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HOWELL EEE TEST FUEL
Certification
ASTM Fuel Specifications Typical
Method Min. Max. Properties
Gravity, API D 1298 59.2
15Reid Vapor Pressure,D 323 8.7 9.2 9.2
psi
Sulfur, wt. % D 3120 0.20 0.001
Lead, g/gal. D 3237 0.0 0.05 0.001
Phosphorus, g/gal. D 3120 0.20 Nil
Distillation, F D 86
20IBP 75 95 92
100 120 135 128
500 200 230 218
95% 300 325 .313
End Point 415 373
25Hydrocarbon CompositionD 1319
Saturates, Vol. % 66.5
Olefins, Vol. % 10 1.8
Aromatics, Vol. % 35 31.7
Existent Gum, mg/100D 381 0.8
ml
30Copper Strip CorrosionD 130 1
Research Octane NumberD 2699 93.0 96.8
Motor Octane Number D 2700 gg_5
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After fleet cars had accumulated 75,000 miles (120,701 km), they were
analyzed for catalyst conversion efficiency -- i.e., the ability of automobile
catalysts
to convert the regulated emissions of hydrocarbons (HC), carbon monoxide (CO)
and
nitrogen oxide (NOx) to non-regulated materials. When compared with conversion
efficiencies of catalysts run on clear test fuel, those run with the manganese-
containing fuel were found to be essentially the same for HC, approximately
1.1
percentage points better for CO, and 3.3 percentage points better for NOx.
Fleet cars were checked after 50,000 miles (80,467 km) for performance of
oxygen sensors. For each model, the oxygen sensors were removed from each auto-
mobile and individually tested. No significant difference occurred in
performance
of the oxygen sensors from cars run on the clear fuel versus cars run on the
same
fuel containing the manganese additive.
Fleet cars were also tested at the end of 75,000 miles (120,701 km) to
determine if catalyst plugging occurred. This was done by measuring the
pressure
level of the exhaust before it enters the catalyst. There was no evidence of
catalyst
plugging on any of the vehicles.
While the base fuel used in the above tests did not comply with the Reid
vapor pressure requirements pursuant to this invention, the above tests
indicate that
cyclopentadienyl manganese tricarbonyl compounds when used in the
concentrations
herein specified, do not cause catalyst plugging nor degrade the performance
of the
automobile emission systems. Thus by reducing the Reid vapor pressure of the
fuel
to the levels specified herein, all of the foregoing benefits can be achieved
while at
the same time reducing the extent to which light ends of the gasoline are
vaporized
into the atmosphere during storage, transportation, and fuel dispensing
operations.
