Note: Descriptions are shown in the official language in which they were submitted.
813-007-0
87/ - 1 -
TITLF, OF THE INVENTION
.
DIESEL FUEL
BACKG~OUND OF THE INVENTION
Field oE the Invention:
This invention relates to fuels for diesel engines
and more particularly to diesel fuel containing ether
additives.
Description of t'ne Prior ~rt:
Frequently, the exhaust emissions from diesel
powered engines contain unacceptable concentrations of
smoke and soot. The tendency for smoke and soot forma-
tion can be reduced by util.izing fuels blended with
ethers and metal salts of organic acids. The salts are
prepared from Group II metals, in particular bariu~l. The
ethers inclucle mono- and di21 Lkyl ethers of glycols,
particularly mono- and dimethyl ethers of ethylene
yl.ycol. However, suc.h admixtures are very expensive and
their e~ectiveness in soot reducti.on is relatively
small. An objectionable feature of the fuels blended
with the salts is that exhaust emissions containing
metals are environmentally unacceptable.
Diesel enyines have also been successfully operated
on diesel fue:L mixed with aLcohols and ethers. The
~lcohols include methanol, ethanol, n-~propanol and n-
hutanol. The greatest advantaye is obtained from fuels
blended with dimethyl ether and methanol. Since blends
containing the above alcohols in concentrations great
enough to achieve desired results are immiscible, it is
necessary to inject the blend components and diesel fuel
separately, e.g., in the intake air and by the usual
injection pumps. Disadvantages are that the calorific
value of the blending components is less than half that
of the diesel and that the cetane number of such mixtures
is greatly reduced or even inadequate or running a
commercial diesel engine smoothly.
Hence a need has continued to exist for a diesel
fuel containing additives which will e~fectively and
economically suppress emissions of smoke and soot from
diesel engines.
SUMM ~Y OF THE_INVENTION
Accordingly, the invention is concerned wlth a diesel
fuel having reduced tendency to cause smoke and soot emissions;
having improved combustion characteristics; and which lncreases
the mechanical efficiency o~ a diesel engine by providing
an improved diesel fuel.
Thus, the invention is also concerned with a miscible
additive for diesel fuel which improves the combustion
characteristics of the fuel and avoids the
difficulties and disadvantages of conventional diesel
fuel additives.
According to the invention, the diesel fuel contains an
additive comprising one or more ethers of the general
formUl~ Rl-o-c(cH3)2-R2~ where Rl and R2 rep
methyl, ethyl, n-propyl, 2-propyl, l-butyl or 2-butyl
group. Additionally, R2 can also be hydrogen. Rl and R2
may or may not be the same. Particularly useful are
methyl-tert-butyl-ether (2-methoxy-2-methyl-propane),
methyl-tert-amyl ether (2-methoxy-2-methyl butane),
isopropyl-tert-butyl ether (2-(2'-propoxy)-2-methyl
propane), sec-butyl-tert-butyl ether (2-(2'-butoxy)-2-
methyl propane), methyl~tert-2,3-~imethylbutyl ether (2-
methoxy-2,3-dimethyl butane) and methyl-tert-~-
methylpentyl ether (2-methoxy-2-methyl pentane).
~hus, the present invention provides a liquid motor
fuel for diesel engines comprising a mixture of a convention-
al hydrocarbon diesel fuel and an additive comprising an
ether having the formula
Rl O-C(CH3)2 ~2~
wherein Rl is an aliphatic radical selected from the group
consisting of methyl, ethyl, l-propyl~ 2-propyl, l-butyl
and 2-butyl groups, and R2 is hydrogen or the same as Rl,
said additive being present in an amount from an amount
effective to improve the combustion properties of said
conventional hydrocarbon diesel fuel up to about 50 volume
~0~315
- 3a ~
percent of said liquid motor fuel.
nETAIrJED DESCRIPTION OF THE INVENTION
AND PREFERRED F.MBODIMENTS
Additive mixtures which contain up to 90% by volume
of one of the above ethers are preferred. Of particular
interest are mixtures containing 5-50% by volume methyl-
tert-butyl ether, 5-50% by volume methyl-tert-amyl ether,
5-50% by volume isopropyl-ter-t-butyl ether, 5-50% by
volume sec-butyl-~ert butyl ether, 5-50~ by volume
methyl-tert-2,3-dimethylbutyl ether, and 5-50~ by volume
methyl-tert-2-methylpentyl ether.
Although blends of gasoline and the above ethers,
particularly methyl-tert-butyl ether, have been success-
fully used in carburetor engines, their usefulness in
upgrading diesel fuels has not been apparent. For
example, on one hand the anti-knock property required
for gasoline i9 not essential for diesel fuel, while on
the other hand, an acceptable self-ignition
ch.~racteristic as well as a defined rate of evaporation
and good solvent properties are required for diesel
fuels.
The favorable effects on diesel properties can
already be shown for ether concentrati.ons as low as 2% by
volume, whereas the preferred minimum concentration of
the ether in the diesel fuel mixture is S~ by volume.
The ethers can be produced by simple methods from llydro-
carbons, which are highly volatile under standard condi-
tions. These hydrocarbons are available in large quan-
tities and are obtained from such sources as petroleum
and rom crude oil and gas processin~. rrhe produced
diesel fuels can contain up to 40~ by volume of ether,
pre~erably up to 25% by volume of ether.
Conventional diesel fuel is a mixture of hydro-
carbons boilin~ within a prescribed range. The many
types of compounds that make up diesel can be grouped
into four broad classes: paraf~inic, naphthenic,
ole~inic and aromatic. An aestlletic problem associated
with the use of liese1 motors is the soot contained in
~o~
--5--
the exhaust emissions, the soot bein~ produced from
cyc]oparaffin.s, and polynuclear arornatics. The amount of
smoke and soot can be decreased with an increase in air-
to-fuel ratio. However, since the volume of the
combustion chambers is fixed, an increasecd air ratio
requires a correspondin~ reduction in fuel rate and,
thus, results in a reduction in energy output.
Ether addition according to the invention greatly
reduces soot formation, thus enabling the quantity of
excess air to be minimized. This, in turn, results in
increased energ~ output. As a result of the reduced air
ratio, the total amount of exhaust emissions is reduced,
resulting in a reduction of ~x as well as soot. Addi-
tionally, markedly lower concentrations of carcinogenic
polycyclic aromatics have been observed.
Since the ethers are essentially sulfur-free, the
sulfur content o~ the blended diesel fuel is decreased.
The lower tendency to Eorm smoke coupled with the lower
sul~ur eontent results in less motor oil oulin~ and thus
in an extended service li~e o~ the motor oil.
When added to diesel fuel, the ether mixtures pro-
duced in accordance with the invention also serve as
solubiliæers for alcohols, in particular for methanol and
ethanol. Alcohols with 1 -to 4 carbon a-toms, i.e.,
methanol, ethanol, isopropanol, butanol, sec-butanol, and
tert-butanol, can be added as pure components or as mix-
tures to the cliesel fuel, in concen~rations o~ ~rom 2 to
~8(:)~9S
--6--
40%, preferably 5 to 25~ by volurne. Since the above
alcohols are miscible in diesel fuel only in low concen-
trations, addition of ethers to the diesel fuel pe~mits
utilization of greater amounts of the above-mentioned
alcohols as diesel fuel components. ~en producing
blends of ethers-alcohols-diesel fuel, the quantity of
ether plus alcohol should not be greater than 60% by
volume of the blended diesel fuel. The preferred blend
contains more than 50~ diesel fuel.
A1thou~h used successfully to produce diesel fuels
containing alcohols, solubilizers, which are produced by
complex processes, are not readily available in large
quantities. In addition, the solubilizers used do not
effect the combustion characteristics of diesel fuel in
the same favorable way as the ethers according to the
invention do.
Having generally described the invention, a more
complete understanding can be obtained by reference to
certain examples, which are provlded herein for purposes
of illustrat.ion onl~ and are not intended to be limiting
unless otherwlse speclfied.
Examples
Specieications for the cornmercial diesel fuel usecl
as the base for blended fuels are shown in Table 1.
_able 1
density (g/ml) 0.~30
f].ash point (C) 80
viscosity (mm /s)4.~6
sulfur (%-wt.) 0.23
calorific value (MJ/kg)42.9
initial/final boiLing point (C) 199-353
residue after distillation (%-vol.) 1.5
cetane number `56.5
. . .
Eight diesel blends containing various amounts of
ethers and/o~ alcohols were prepared. Compositions and
analyses of these samples are shown in Table 2.
lable 2
.. . . . .. .
Ex Fuel Density Sul- Viscos- C~lori- Cetane
am~ Con~c- fur ity fic numker
ple sition value
(~ wt) ( s ) ( ~ kg~
1 50 DF ~ 50 Bl 0.793 0.12 1.53 39.87 40*
2 43 DF ~ 32 Bl -~
29 M 0.798 0.10 1.69 35.24
3 50 DF ~ 25 B1 +
25 E 0.804 0.12 2.05 37.19 45*
4 90 DF + 10 Bl 0.821 0.21 3.43 42.46 49.5
78.5 DF ~ 16.5 81 +
5 M 0.815 0.18 2.70 40~91 41.0
6 81 DF t 14 Bl ~ 5E 0~817 0.1~ 2.94 41.11 42~0
7 50 DF ~ 50 E~ 0.778 0.11 1.78 40.43 45*
8 90 DF -~ 10 B2 0.822 0.21 3.50 42.38 49.5
Legend:
DF Basic component as per Table 1
Bl Mixt~e of
90~ ~y volume methyl-tert-but~l ether, isopropyl-tert--butyl
etherp sec-butyl-tert-butyl ether (volume ratio 1:1:1), plus
10~ ~y volume methanol, i~opropanol, sec-but~nol (volume ratio
1:1:1)
B2 ~ec-butyl--tert--butyl ether
M Methanol
E~hanol
*I To accelerate ignition, di-sec-butyl-para-phenylenedianine was
added -to three exa~ples. The examples and amount added to each
are: 0.5% by weight to Example 1, 3.5% ~y weight to Example 3
and 2.0% by weight to Exa~ple 7.
The test runs comparing the diesel fuel of the
invention with commercial fuels were carried out with
commercial diesel engines: Daimler Benz*Type 240 D and
Volkswagen (VW) Type Gol~ D. For all tests, the engines
were operated at fixed rotational speeds of 4400 rpm for
the Daim]er Benz 240 D and 4800 rpm for the VW Golf D.
Engine operation was adjusted such that the performance
~or each test was equivalent to tllat of the engines when
operating on commercial diesel fuel.
The exhaust gas blackness and specific energy con-
sumption were determined using a Daimler Benz engine Type
240 D operating at 4400 rpm and 47.3 kW. The blackness
is repor~ed as Bosch*Number (BN). Table 3 shows the
Bosch Number and specific energy requirements determined
in tests using commercial diesel fuel, Example 0, and
blends, Examples 1 through 8. The compositions of
Examples 1 through 8 are shown in Table 2.
*11rad~ Mark
~L8~
--10--
Table 3
-
Example BN SpeciÆic Energy
Consumption
(MJ/kWh)
0 ' 2.1 15.98
]. 1.2 16~00
2 0.8 15.06
3 0.8 15.22
4 1.3 15.73
1.4 15.80
~ 1.1 15.30
7 0.9 15.54
~ 1~4 15.8~
Table 3 reveals that soot formation from the blended
fuels according to the invention is much less than that
from commercial cliesel fuel. A~s shown, the reduction in
soot formation ranges ~rom 32~ to 62~. Also, as shown by
Example 4, which is 90~ by volume diesel fuel, small
amounts of et,her-alcohol greatly reduce soot formation.
In ~xample 4, .soot formation has 'been reduced by 38~.
Irrespective of the lower calorific value o~ the
mi.xtures according to the invention, it can be seen that
the specific energy consumption is oE the same level or
in most cases even lower than when using the basic diesel
fuel.
~ commercial VW type Golf D engine operating at 31.4
kW and a speed of 4800 rpm was used to evaluate the
effect oE ether-alcohol blends on the concentrat.ion of
N0x in the exhaust emissions. The results of these te~sts
are showll in Table ~.
s
Table 4
Fuel N0x (ppm)
0 500
1 370*
2 440*
3 430*
4 470
41~
6 450
7 380
8 S00
*To accelerate ignition, di-sec-butyl-para phenylene-
diamine was added to Examples 1, 2 and 3. The amounts
added were 1.0% by volume to Example 1, 2,5~ by volume to
Exarnple 2, and 1.5~ by volume to Example 3.
~s shown in Table 4, the diesel blends according to
the invention reduce the N0x concentrations in the
exhaust gases up to 26% in comparison with conventional
diesel fuel.
~laving now ~ully described the invent.ion, it will be
a~parent to one o~ ordinary skill in the art that many
chanc3es and modifications can be made thereto without
departing from the spirit or scope of the invention as
set forth herein.
