Note: Descriptions are shown in the official language in which they were submitted.
2~ ~ ~ 8~ PATENTS
CASE: EI 6393
DEL:smd
FUEL COMPOSITIONS
This invention relates to preservation of the
environment. More particularly, this invention relates to fuel
compositions and methods that reduce atmospheric pollution
normally caused by the operation of engines or combustion
apparatus on middle distillate fuels.
The importance and desirability of reducing the release
of pollutants into the atmosphere are well recognized. Among the
pollutants sought to be reduced are nitrogen oxides ("NO~"),
carbon monoxide, unburned hydrocarbons, and particulates.
This invention involves the discovery, inter alia, that
it is possible to reduce the amount of NO~ or CO or unburned
hydrocarbons released into the atmosphere during operation of
engines or other combustion apparatus operated on a fuel compo-
sition characterized in that it comprises a major proportion of a
hydrocarbonaceous middle distillate fuel which has a sulfur con-
tent of less than 500 ppm and in that said fuel contains a minor
emission reducing amount of ~i) at }east one organic nitrate
combustion improver, and (ii) at least one tertiary alkyl peroxy
alkanoate or peroxy benzoate dissolved therein. In fact it has
~ been found possible through use of such fuel compositions to
reduce the amount of two and in some cases all three such pollu-
tants (NO~, CO and unburned hydrocarbons) emitted by diesel
engines. Moreover this important and highly desirable ob3ective
has been and thus may be achieved without suffering an undesir-
able increase in the emission of particulates. This is a unique
discovery since the available experimental evidence and
mechanistic theories of combustion suggest that i~ NO~ is
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CASE: EI-6393
reduced, the amount of particulates will be increased, and vice
versa.
Accordingly this invention provides in one of its
embodiments a fuel composition characterized in that it comprises
a major proportion of a hydrocarbonaceous middle distillate fuel
which has a sulfur content of less than 500 ppm (preferably 100
ppm or less and most preferably no more than 60 ppm) and in that
said fuel contains a minor emission reducing amount of (i) at
leaet one organic nitrate combustion improver and (ii) at least
one tertiary alkyl peroxy alkanoate or peroxy benzoate of the
formula
R - 0 - 0 - C - R'
dissolved therein wherein R is a tertiary alkyl group of 4 to 8
carbon atoms and R' is a hydrocarbon group having 1 to 24 carbon
atoms.
By the term "hydrocarbonaceous" as used in the ensuing
description and appended claims is meant the middle distillate
fuel is composed principally or entirely of fuels deri~e~ from
petroleum by any of the usual processing operations. The
finished fuels may contain, in addition, minor amounts of
non-hydrocarbonaceous fuels or blending components such as
alcohols, or like materials, and/or minor amounts of suitably
~ desulfurized auxiliary liquid fuels of appropriate boiling ranges
(i.e., between about 160 and about 370C) derived from tar
sands, shale oil or coal. When using blends composed of such
desulfurized auxiliary liquid fuels and hydrocarbonaceous middle
CASE: EI-6393
distillate fuels, the sulfur content of the total blend must be
kept below 500 ppm.
In another of its embodiments this invention provides
improvements in combustion processes wherein a hydrocarbonaceous
middle distillate fuel is subjected to combustion in the presence
of air. Such improvement comprises providing as a fuel used in
such process a hydrocarbonaceous middle distillate fuel having a
sulfur content of less than 500 ppm (preferably 100 ppm or less
and most preferably no more than 60 ppm) and having dissolved
therein a minor emission-reducing amount of (i) at least one
organic nitrate combustion improver, and (ii) at least one
tertiary alkyl peroxy alkanoate or peroxy benzoate of the formula
R - 0 - 0 - C - R'
0
wherein R is a tertiary alkyl group of 4 to 8 carbon atoms and R'
is an aliphatic or aromatic hydrocarbon group having 1 to 24
carbon atoms and wherein the organic nitrate combustion improver
comprises a nitrate ester of a substituted or unsubstituted
aliphatic or cycloaliphatic alcohol.
Still another em~odiment of this invention provides
improvements in the production of hydrocarbonaceous middle dis-
tillate fuels. Such improvements comprise controlling or re-
ducing the sulfur content of the fuel to a level of 500 ppm or
less (preferably 100 ppm or less and most preferably no more than
60 ppm) and blending with the resultant reduced sulfur-containing
fuel, (i) at least one organic nitrate combustion improver, and
(ii) at least one tertiary alkyl peroxy alkanoate or peroxy
~enzoate of the formula
2~ 4~ CASE: EI-6393
R - o - o - C - R'
wherein R is a tertiary alkyl group of 4 to 8 carbon atoms and R'
is an aliphatic or aromatic hydrocarbon group having 1 to-24
carbon atoms and wherein the organic nitrate combustion improver
comprises a nitrate ester of a substituted or unsubstituted
aliphatic or cycloaliphatic alcohol.
Additional embodiments of this invention involve -
improvements in the operation of motor vehicles and aircraft
which operate on middle distillate fuels. These improvements
involve fuelin~ the vehicle or aircraft with a hydrocarbonaceous ,
middle distillate fuel characterized by having a sulfur content
of less than 500 ppm (preferably 100 ppm or less and most
preferably no more than 60 ppm) and containing (i) at least one
organic nitrate combustion improver, and (ii) at least one
tertiary alkyl peroxy alkanoate or peroxy benzoate of the formula
R - 0 - 0 - C - R'
o
dissolved therein wherein R is a tertiary alkyl group of 4 to 8
carbon atoms and R' is an aliphatic or aromatic hydrocarbon group
having 1 to 24 carbon atoms and wherein the organic nitrate
combustion improver comprises a nitrate ester of a substituted or
unsubstituted aliphatic or cycloaliphatic alcohol.
In accordance with a particularly preferred embodiment
of this invention, there is provided a hydrocarbonaceous middle
distillate fuel having a sulfur content of not more than 500 ppm
(preferably 100 ppm or less and most preferably no more than 60
ppm) and a 10~ boiling point (ASTM D-86) in the range of about
154 to about 230CC~ said fuel containing a minor emission-
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CASE: EI-6393
reducing amount of (i) at least one fuel-soluble organic nitrate
combustion improver, and (ii) at least one tertiary alkyl peroxy
alkanoate or peroxy benzoate of the formula
R - 0 - 0 - C - R'
wherein R is a tertiary alkyl group of 4 to 8 carbon atoms and ~'
is an aliphatic or aromatic hydrocarbon group having 1 to 24
carbon atoms and wherein the organic nitrate combustion improver
comprises a nitrate ester of a substituted or unsubstituted
aliphatic or cycloaliphatic alcohol. Such fuel compositions tend
on combustion to emit especially low levels of N0~. Without
desiring to be bound by theoretical considerations, one
explanation for such highly desirable performance is that fuels
with higher 10% boiling points cause a delay in the progression
of combustion and consequent higher peak temperatures which
increase the amount of N0% formation.
These and other embodiments are set forth in the
ensuing description and appended claims.
The hydrocar~onaceous fuels utilized in the practice o
this invention are comprised in general of mixtures of hydro-
carbons which fall within the distillation range of about 160 to
about 370C. Such fuels are frequently referred to as "middle
~5 distillate fuels" since they comprise the fractions which distill
after gasoline. Such fuels include diesel fuels, burner fuels,
kerosenes, gas oils, jet fuels, and gas turbine engine fuels.
Preferred middle distillate fuels are those charac-
terized by having the followinq distillation profile:
2~ 78 ~ ~ CASE: EI-6393
F oc
IBP 250 - 500 121 - 260
10% 310 - 550 154 - 288
50% 350 - 600 177 - 316
90% 400 - 700 204 - 3?1
EP 450 - 7S0 232 - 399
Diesel fuels having a clear cetane number (i.e., a
cetane number when devoid of any cetane improver such as an
organic nitrate) in the range of 30 to 60 are preferred.
Particularly preferred are those in which the clear cetane number~
is in the range of 40 to 50.
The organic nitrate combustion improvers (also fre-
quently known as ignition improvers) comprise nitrate esters of
substituted or unsubstituted aliphatic or cycloaliphatic alcohols
which may be monohydric or polyhydric. Preferred organic
nitrates are substituted or unsubstituted alkyl or cycloalkyl
nitrates having up to about 10 carbon atoms, preferably from 2 to
10 carbon atoms. The alkyl group may be either linear or
branched (or a mixture of linear and branched alkyl groups).
Specific examples of nitrate compounds suitable for use in the
present invention include, but are not limited to, the following:
methyl nitrate, ethyl nitrate, n-propyl nitrate, isopropyl
nitrate, allyl nitrate, n-butyl nitrate, isobutyl nitrate, sec-
butyl nitrate, tert-butyl nitrate, n-amyl nitrate, isoamyl
2S nitrate, 2-amyl nitrate, 3-amyl nitrate, tert-amyl nitrate,
n~hexyl nitrate, n-heptyl nitrate, sec-heptyl nitrate, n-octyl
nitrate, 2-ethylhexyl nitrate, sec-octyl nitrate, n-nonyl
nitrate, n-decyl nitrate, cyclopentylnitrate, cyclohexyl nitrate,
methylcyclohexyl nitrate, isopropylcyclohexyl nitrate, and the
like. Also suitable are the nitrate esters of alkoxy substituted
~ - 6 -
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CASE: EI-6393
aliphatic alcohols such as 2-ethoxyethyl nitrate, 2-(2-ethoxy-
ethoxy)ethyl nitrate, 1-methoxypropyl-2-nitrate, 4-ethoxybutyl
nitrate, etc., as well as diol nitrates such as 1,6-hexamethylene
dinitrate, and the like. Preferred are the alkyl nitrates havinq
from 5 to 10 carbon atoms, most especially mixtures of primary
amyl nitrates, mixtures of primary hexyl nitrates, and octyl
nitrates such as 2-ethylhexyl nitrate.
As is well known, nitrate esters are usually prepared
by the mixed acid nitration of the appropriate alcohol or diol.
Mixtures of nitric and sulfuric acids are generally used for this
purpose. Another way of ma~ing nitrate esters involves reacting
an alkyl or cycloalkyl halide with silver nitrate.
The concentration of nitrate ester component in the
fuel can be varied within relatively wide limits with the proviso
that the amount employed, when in combination with at least one
tertiary alkyl peroxy alkanoate or peroxy benzoate, is at least
sufficient to cause a reduction in emissions. Generally
speaking, the of amount of nitrate ester employed will fall in
the range of about 2$0 to about 10,000 parts by weight of organic
nitrate per million parts by weight of the fuel. Preferred
concentrations usually fall within the range of S00 to 2000 parts
per million parts of fuel.
The tertiary alkyl peroxy alkanoates or peroxy benzo-
ates used in the practice of this invention contain at least ~
carbon atoms in the molecule, and prefera~ly the tertiary alkyl
group, R above, contains 4 to 8 carbon atoms and the hydrocarbon
group, ~' above, is a substantially saturated aliphatic hydro-
carbon group or an unsubstituted aromatic group. The tertiary
alkyl peroxy alkanoates or peroxy benzoates may be used singly
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CASE: EI-6393
with the nitrate ester component or two or more alkanoate or
benzoate compounds may be used in combination with the nitrate
ester component. Illustrative peroxy esters include tert-butyl
peroxy-acetate, tert-butyl peroxy-butylate, tert-butyl peroxy-
hexanoate, tert-butyl peroxy-heptanoate, tert-butyl peroxy-
octanoate, tert-butyl peroxy-decanoate, tert-butyl peroxy-
dodecanoate, tert-butyl peroxy-tetradecanoate, tert-butyl peroxy-
hexadecanoate, tert-butyl peroxy-octadecanoate, tert-butyl
peroxy-eicosanoate, tert-butyl peroxy-tetracosanoate, tert-butyl
peroxy-hexadecenoate, tert-butyl peroxy-octadecenoate, tert-butyl
peroxy-2-methylhexanoate, tert-butyl peroxy-3-methylhexanoate,
tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-octyl-
octanoate, tert-butyl peroxy-2,7-dimethyloctanoate, tert-butyl
peroxy-benzoate and like compounds in which the tertiary alkyl
group is tert-amyl, 1,1,2-trimethylpropyl, 1,1,3,3-tetra-methyl-
butyl or the like.
The base fuel will normally contain an amount in the
range of 100 to about 50,000 and preferably, from about 500 to
about 2,000 -- parts of the tertiary alkyl peroxy alkanoate or
peroxy benzoate component per million parts by weight of the base
fuel (ppm). SucA quantities are normal~y sufficient, when in
combi-nation with a substantially similar amount of organic
nitrate combustion improver, to reduce the amount of diesel
emission as compared to amount of emission that occurs in the
same engine operated under the same conditions on the same fuel
composition absent the emission-reducing additive of this
invention.
Other additives may be included within the fuel
compositions of this invention provided they do not adversely
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CASE: EI-6393
of this invention. Thus use may be made of such components as
organic peroxides and hydroperoxides, corrosion inhibitors,
antioxidants, anti-rust agents, detergents and dispersants,
friction reducing agents, demulsifiers, dyes, inert diluentQ, and
like material~.
The advantages achievable by the practice of this
invention were demonstrated in a sequential series of engine
tests in which a Detroit Diesel 11.1 liter Series 60 engine
mounted to an engine dynamometer was used. The system was
operated on the "EPA Engine Dynamometer Schedule for Heavy-Duty
Diesel Engines" set forth at pages 810-819 of Volume 40, Part 86,
Appendix I, of the Code of Federal Regulations (7-1-86). In
these tests, the first of nine consecutive tests involved opera-
tion of the engine on a conventional DF-2 diesel fuel having a
nominal sulfur content in the range of 2000 to 4000 ppm. This
test served as one of two baselines. In the next operation the
engine was run using a low-sulfur diesel fuel having the follow-
lng characteristics:
Sulfur, ppm 50
Gravity, API ~ 60F 34.7
Pour Point, F -5
Cloud Point, F R
Copper Strip
Distillation, F
IBP 332
10% 430
50% 532
90% 632
EP 634
Cetane Number 44.3
Viscosity @ 40C, cS 2.96
In the third and fourth tests this same low-sulfur fuel
was used excopt that it had ~lended therein a diesel ignition
_ q
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CASE: EI-6393
improver composed of 2-ethylhexyl nitrate. In the third test the
concentration was 2000 ppm of the organic nitrate. In the fourth
test, the fuel contained 5000 ppm of the organic nitrate. The
fifth involved another baseline run using the initial conven-
tional DF-2 diesel fuel. In the sixth test another unadditized
low sulfur fuel was run. The same low sulfur fuel was run in the
seventh test except that the fuel contained 1250 ppm of ~he
organic nitrate and 1250 ppm of the peroxy ester (tert-butyl
peroxy-2-ethylhexanoate). In the eighth test a different unaddi-
tized low sulfur fuel was run. The ninth and final test con-
tained the same fuel as in run eight, except that it contained
500 ppm of the organic nitrate and 500 ppm of the peroxy ester.
In all instances the quantities of NO~, un~urned hydrocarbons
("HC"), carbon monoxide ("C0") and particulates emitted by the
engine were measured and integrated. The results of these tests
are summarized in the following table. The values shown therein
for N0~, HC, C0, and particulates, are presented in terms of
grams per brake horsepower per hour. Thus the lower the value,
the lower the rate and amount of emissions.
Test No. NOx HC C0 Particulates
14.641 0.086 1.414 0.227
24.345 0.068 1.490 0.165
34.173 0.051 1.312 0.164
44.208 0.073 1 324 0.165
54.623 0.078 1.525 0.223
' 64.270 0.224 1.600 0.153
; 74.220 0.141 1.290 0.156
84.3~0 0.157 1.480 0.154
94.310 0.114 1.290 0.170
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CASE: EI-6393
In particularly preferred em~odiments of this inven-
tion, use of fuels having certain boiling characteristics as well
as low sulfur levels, results in still further reductions in
either NOX or particulate emissions. Thus by use of fuels meet-
ing the low sulfur parameters set forth hereinabove and addition-
ally having a 10% boiling point (AS~M D-86) in the range of
lS4-230C, the emissions of N0x can be reduced to extremely low
levels. Likewise, by use of fuels meeting the low sulfur para-
meters set forth hereinabove and additionally having a 90%
boiling point (ASTM D-86) in the range of 260-320C, particulate
emissions tend to be reduced to especially low levels. To
illustrate, a Detroit Diesel Corporation Series 60 Engine in the
11.1 liter configuration and nominally rated at 320 hp at 1800
rpm was used in a series of emission tests. The engine was
installed in a heavy-duty transient emission cell equipped with a
constant volume sampler (CVS) system. A dilution tunnel
permitted measurements of H~, C0, N0x and particulates according
to the EPA Transient Emissions Cycle Procedure.
For each individual test case, the engine was started
and warmed up. It was then run for 20 minutes at rated speed and
load~ Rated power was va}idated. In addition, a power test was
conducted, mapping engine torque vs. speed. These parameters are
required as part of the EPA Transient Cycle Procedure. once this
information was obtained, two 20-minute EPA Transient Cycles were
` run and engine controls were adjusted to meet statistical operat-
ing limits prescribed for the tests. The engine was shut down
and allowed to soak for 20 minutes. At the end of the soak
period, the Hot Start EPA Transient Cycle was run to measure N0x,
C0 and particulate emissions. A second emissions evaluation was
conducted after another two-minute soak. Results for the two Hot
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CASE: EI-6393
Transient Cycles were averaged into a final reported value.
Whenever a fuel was changed, new fuel was introduced into the
fueling system, new fuel filters were installed, and fuel lines
were flushed.
Each fuel (A through D) was evaluated by the same Hot
Start EPA Transient Emissions Cycle Procedure. Fuels A, B, and C
contained 2-ethylhexyl nitrate in an amount sufficient to raise
the cetane number of the respective fuels to a nominal value of
50. Fuel D which had a natural cetane number of 49.8 was used
unadditized.
Physical and chemical characterization data for
unadditized fuels A through D are shown in the following table:
~BLE
Fuel Pro~ertv A B C D
Hydrocarbon Composition, vol %
Aromatics 36.5 28.5 37.6 39.4
Olefins 1.2 1.1 2.2 2.9
Saturates 62.3 70.4 60.2 57.7
Carbon, wt~ 86.3586.49 86.12 87.32
Hydrogen, wt% 13.1513.25 12.89 13.35
Nitrogen, ppm 5.3 285 356 152
Sulfur, ppm <1 225 219 476
Aniline pt., deg. C 70.1 60.0 65.4 69.4
~ Diene content, wt~ <0.1 0.2 ~0.1 <0.1
Viscosity, cSt
Q 40 deg. C 2.99 2.20 3.10 3.53
@ 100 deg. C 1.22 0.97 1.23 1.34
Heat of combustion B~U/lb19,593l9,R4019,543 19,672
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CASE: EI-6393
Boiling range, deg. C
IBP 170 172 202 218
10% 217 211 234 252
20% 233 222 246 262
30% 249 230 257 271
40~ 262 237 267 278
50% 274 244 276 284
60~ 288 253 286 291
70% 300 263 294 298
80% 314 276 306 306
9o% 331 297 322 317
95% 344 319 338 329
FBP 352 334 353 341
Recovery, % 98.7 98.9 98.6 98.9
lS Gravity, deg. API 34.9 36.1 34.6 34.5
Specific gravity 0.850 0.844 0.852 0.852
Calculated cetane index48.144.0 48.9 51.7
Cetane index 48.5 43.8 48.3 49.7
Cetane number 45.3 39.6 47.7 49.8
In the above table, the following test methods were used:
Hydrocarbon composition - ASTM D-1319
Carbon - Carlo-Erba 1106
Hydrogen - Carlo-Erba 1106
Nitrogen - ASTM D-4629
2S Sulfur - ASTM D-3120
Aniline pt. - ASTM D-611
Diene content - UOP 326
Viscosity - ASTM D-445
Heat of combustion - ASTM D-2382
~oiling range - ASTM D-86
Gravity - ASTM D-287
Calculated cetane index - ASTM D-4737
Cetane index - ASTM D-976
Cetane number - ASTM D 613
3S Methods for reducing the sulfur content of hydrocar-
~onaceous middle distillate ~uels or their precursors are
reported in the literature and are otherwise available to those
skilled in the art. Among such processes are solvent extraction
.
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CASE: EI-6393
using such agents as sulfur dioxide or furfural, sulfuric acid
treatment, and hydrodesulfurization processes. Of these,
hydrodesulfurization is generally preferred, and includes a
number of specific methods and operating conditions as applied to
various feedstocks. For example, hydrotreating or
hydroprocessing of naphthas or gas oils is generally conducted
under mild or moderate severity conditions. On the other hand,
sulfur removal by hydrocracking as applied to distillate stocks
is usually conducted under more severe operating conditions.
Vacuum distillation of bottoms from atmospheric distillations is
still another method for controlling or reducing sulfur content
of hydrocarbon stoc~s used in the production of hydrocarbonaceous
middle distillate fuels. Further information concerning such
processes appears in Kirk-Othmer, Encvclo~edia of Chemical
lS Technoloqy, Second Edition, Interscience Publishers, Volume 11,
pages 432-445 (copyright 1966) and references cited therein;
~, Volume 15, pages 1-77 and references cited therein; and
Kirk-Othmer, Encyclopedia of Chemical Technoloay, Volume 17,
Third Edition, Wiley-Interscience, pages 183-256 (copyright 1982)
and references cited therein. All of such publications and cited
references are incorporated herein by reference in respect of
processes or methods for control of reduction of sulfur content
in hydrocarbonaceous middle distillate fue}s or their precursor
stocks.
Another method which can be used involves treatment of
the hydrocarbonaceous middle distillate fuel with a metallic
desulfurization agent such as metallic sodium, or mixtures of
sodium and calcium metals.
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CASE: EI-6393
This invention is applicable to the operation of both
stationary diesel engines (e.g., engines used in electrical power
generation installations, in pumping stations, etc.) and in
ambulatory diesel engines (e.g., engines used as prime movers in
automobiles, trucks, road-qrading equipment, military vehicleq,
etc.).
Other similar embodiments of this invention will - ;
readily occur to those skilled in the art from a consideration of
the foregoing disclosure.
This invention is su~ceptible to considerable variation
in its practice without departing from the spirit and scope-of
the ensuing claims.
