Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HYDROXY AMINE FUEL COMPOSITION
This invention relates to the use of an additive for providing a low sulphur
fuel oif
with improved lubricity and other benefits and to fuel oil compositions
containing
the additives.
US A-4,409,000 describes additives for normally liquid fuels for providing
carburettor and engine detergency. A combination of at least one hydroxyl
amine
of specified formula and at least one hydrocarbon soluble carboxylic
dispersant is
to proposed for inhibiting the formation of sludge in the carburettor and
engine. The
sole exemplification relates to the use of such combinations of ingredient in
gasoline. Apart from the statement that the compositions provide carburettor
and
engine detergency no ether information is provided as to properties provided
by
these compositions.
~s
US-A-2,527,889 describes polyhydroxy alcohol esters as primary anti-corrosion
additives in diesel engine fuel, and GB A-1,505,302 describes ester
combinations
including, for example, glycerol monoesters and glycerol diesters as diesel
fuel
additives, for combinations being described as leading to advantages.
including
20 less wear of the fuel-injection equipment, piston rings and cylinder
liners.
GB-A-1,505,302 is, however, concerned with overcoming the operational
disadvantages of corrosion and wear by acidic combustion products, residues in
the combustion chamber and in the exhaust system. The document states that
2s these disadvantages are due to incomplete combustion under certain
operating
conditions. Typical diesel fuels available at the date of the document
contained,
for example, from 0.5 to 1 % by weight of sulphur, as elemental sulphur, based
on
the weight of the fuel.
ao The sulphur content of diesel fuels has now been or will be lowered in a
number
of countries for environmental reasons, I.e. to reduce sulphur dioxide
emissions.
Thus, heating oil and diesel fuel sulphur content are being harmonised by the
CEC at a maximum of 0.2% by weight, and; at a second stage, the maximum
content in diesel fuel will be 0.05% by weight. Complete conversion to the
0.05%
ss maximum may be required during 1996.
The process for preparing low sulphur content fuels, in addition to reducing
sulphur intent, also reduces the content of other components of the fuel such
as
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polyaromatic components and polar components. Reducing one or more of the
sulphur, polyaromatic and polar component content of the fuel creates a new
problem in use of the fuel, i.e. the ability of the fuel to lubricate the
injection
system of the engine is reduced such that, for example, the fuel injection
pump of
the engine can fail relatively early in the life of an engine, failure being,
e.g. in
rotary distributor pumps, in high pressure fuel injection systems such as high
pressure rotary distributors, in-line pumps and unit injectors and injectors.
Such
severe failures are not due to corrosive wear as described in GB-A-1,505,302.
~o As stated, such failure can occur early in the life of an engine; in
contrast, the
wear problems referred to in GB-A-1,505,302 occur late in the life of an
engine.
The problem created by adopting low sulphur content diesel fuels is described
in,
for example D. Wei and H. Spikes, Wear, Vol. 111, No. 2, p. 217, 1986; and
R. Caprotti, C. Bovington, W. Fowler and M. Taylor, SAE Paper 922183; SAE
fuels and tubes meeting Oct. 1992; San Francisco, USA.
It has now been found that the above-mentioned wear problem due to use of
fuels
having a low sulphur content can be lessened or met by providing certain
additives in the fuel. Additional benefits also arise from the use of the same
2o additives.
According to the present invention there is provided a fuel oil composition
comprising a major proportion of a liquid hydrocarbon middle distillate fuel
oil
having a sulphur content of not greater than 0.2% by weight of the fuel oil
and a
minor proportion of at least one hydroxy amine of formula.
R2 R3
(CH - CH)P O H
/ a
R~-N
(CH - CH)q O H
b
R4 R5
where R1 is an alkenyl radical having one or more double bonds or an alkyl
ao radical and containing from 4 to 50 carbon atoms, or a radical of the
formula:
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Rs R7
(CH - CH)" O H
/ c
R8N
R9
where each of R2, R3, R4, R5, R6 and R7 is independently hydrogen or a lower
s alkyl radical; R8 is an alkenyl radical having one or more double bonds or
an alkyl
radical and containing from 4 to 50 carbon atoms; R9 is an alkylene radical
containing from 2 to 35, e.g. 2 to 6, carbon atoms; each of p, q and v is an
integer
between 1 and 4; and each of a, b and c may be 0, providing that at least one
of
a, b or c is an integer between 1 and 75.
15
A second aspect of the invention is the use of a fuel oif composition as
defined in
the first aspect of the invention as the fuel in a compression-ignition
(diesel)
engine for controlling wear rate in the injection system of the engine in
operation
of the engine.
A third aspect of the invention is a method of operating a compression-
ignition
(diesel) engine comprising providing a fuel oil composition as defined in the
first
aspect of the invention as the fuel in the engine thereby to control wear rate
in the
injection system of the engine.
According to an aspect of the present invention, there is provided a fuel
oil composition comprising a major proportion of a liquid hydrocarbon
middle distilate fuel oil having a sulphur content or not great than 0.2%
by weight of the fuel oil and a minor proportion of at least one hydroxy
2s amine of formula.
In one embodiment, the concentration of hydroxy amine is from 1 ppm to
2000ppm by weight of the fuel oil.
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The examples of this specification will demonstrate the efficacy of the
hydroxy
amine additives defined under the first aspect of the invention in reducing
wear
when fuel oils having a sulphur content of not greater than
0.2°!° by weight are
used.
Whilst not wishing to be bound by any theory, it is believed that the
additive, in
use of the composition in a compression-ignition internal combustion engine,
is
1o capable of forming over the range of operating conditions of the engine, at
least
partial mono- or multi-molecular layers of the additive on surfaces of the
injection
system, particularly the injector pump that are in moving contact with one
another,
the composition being such as to give rise, when compared with a composition
lacking the additive, to one or more of a reduction in wear, a reduction in
friction,
or an increase in electrical contact resistance in any test where two or more
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loaded bodies are in relative motion under non-hydrodynamic lubricating
conditions.
The inclusion of the additive in the fuel oil has been found to give rise to
the
s further advantage that the tendency of the fuel oil to foam is markedly
reduced,
whereby the antifoaming agents conventionally added thereto may be reduced or
even eliminated.
The features of the invention will now be described in further detail.
ADDITIVE
As stated, it is believed that the additive, which may be a single hydroxy
amine
1s compound or mixture of compounds, is capable of forming at least partial
layers
on certain surfaces of the engine. By this is meant that the layer formed is
not
necessarily complete on the contacting surface. Thus, it may cover only part
of
the area of that contacting surface, for example 10% or more, or 50% or more.
The formation of such layers and the extent of their coverage of a contacting
2o surface can be demonstrated by, for example, measuring electrical contact
resistance or electrical capacitance.
An example of a test that can be used to demonstrate one or more of a
reduction
in wear, a reduction in friction or an increase in electrical contact
resistance
2s according to this invention is the High Frequency Reciprocating Rig test
which will
be referred to hereinafter.
The hydroxy amine compounds identified above as suitable for use in the
invention must contain a group, R1 or R8, attached to a nitrogen atom which is
an
so alkyl or alkenyl group having one or more double bonds, containing 4 to 50,
preferably 8 to 30, and more preferably 12 to 25 carbon atoms. The hydroxy
functionality is provided by at least one hydroxy alkyl group attached to a
nitrogen
atom, either directly (as illustrated, for example, by the moiety
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R2 R3
11
(CH - CH)p O H _
a
when a is 1, or indirectly via an oxyalkylene or polyoxyalkylene linking group
(when, for example, a is 2 or more. The hydroxy alkyl group and the
oxyalkylene
s units of any linking group may contain from 2 to 6 carbon atoms, optionally
substituted with lower alkyl radicals. By 'lower' alkyl is meant an alkyl
group
containing 6 or less carbon atoms. Preferably, p, q and v, if present, are
equal to
1.
1o The hydroxy alkyl group and the oxyalkylene units of any linking group may
together form a chain having up to 75 units including the terminal hydroxy
alkyl
group. Preferably the number of oxyalkylene units does not exceed 10. The most
preferred number represented by a, b and c in the structural formula is 1 for
each
of a, b and when present, c.
The radicals R2, R3, R4, R5, R6 and R7 are preferably hydrogen or methyl.
In the structural formula, R9, if present, is preferably an alkylene radical
containing
from 2 to 6 carbon atoms, which may be a straight or branched chain of carbon
2o atoms.
Suitable hydroxy amines may be prepared by reaction of amine, substituted with
an appropriate R1 or R$ group and having residual amine functionality, with an
alkylene oxide, such as ethylene oxide or propylene oxide. Suitable
ethoxyamines
are commercially available from Annak Company under the trade names
'Ethomeen' and 'Ethanolomeen'. TM
The concentration of hydroxy amine which is effective in sign~cantly improving
the
lubricity of the fuel is extremely low and may readily be determined by the
wear
so tests identified in the Examples. In general, a noticeable reduction in
wear is
observed using as little as 5 ppm of additive by weight of fuel. Preferred
concentrations range from 10 ppm to 0.2% by weight. Although higher
concentrations may be used the wear test should be used to determine the
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optimum concentration. For reasons of economics the minimum effective amount
should be used. A concentration between 25 ppm and 1000 ppm is preferred.
Noticeable reductions in foaming tendency of the fuel are observed at even
lower
s concentrations of the additive and as little as 1 ppm can have a significant
foam
reducing effect.
FUEL OIL
~o
The additives of the invention are effective when used with a liquid
hydrocarbon
middle distillate fuel oil containing not greater than 0.2% by weight of
sulphur.
Preferably, the sulphur concentration is 0.05% by weight or less, such as 0.01
15 by weight or less, and may be as low as 0.005% by weight, or 0.0001 % by
weight,
or lower. The art describes methods of reducing the sulphur concentration of
hydrocarbon distillate fuel oils, such methods including for example solvent
extraction, sulphuric acid treatment, and hydrodesulphurisation.
2o Middle distillate fuel oils to which this invention is applicable generally
boil within
the range of about 100°C to about 500°C, e.g. about 150°C
to about 400°C. The
fuel oil can comprise atmospheric distillate or vacuum distillate, or cracked
gas oil
or a blend in any proportion of straight run and thermally and/or
catalytically
cracked distillates. The most common petroleum distillates are kerosene, jet
2s fuels, diesel fuels, heating oils and heavy fuel oils, diesel fuels being
preferred in
the practice of the present invention for the above-mentioned reasons. The
heating oil may be a straight atmospheric distillate, or it may contain
amounts, e.g.
up to 35% by weight of vacuum gas oil or of cracked gas oils or of both.
ao The additive may be incorporated into bulk fuel oil by methods known in the
art.
Conveniently, the additive may be so incorporated in the form of a concentrate
comprising an admixture of the additive and a liquid carrier medium compatible
with the fuel oil, the additive being dispersed in the liquid medium. Such
concentrates preferably contain from 3 to 75 wt %, more preferably 3 to 60 wt
%,
as most preferably 10 to 50 wt % of the additive, preferably in solution in
the oil.
Examples of carrier liquid are organic solvents including hydrocarbon
solvents, for
example petroleum fractions such as naphtha, kerosene and heater oil; aromatic
hydrocarbons; paraffinic hydrocarbons such as hexane and pentane; alkahols;
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isoparaffins; and alkoxyalkanols. The carrier liquid must of course be
selected
having regard to its compatibility with the additive and with the fuel.
s CO-ADDITIVES
The additives of the invention may be used singly or as mixtures of more than
one
additive. They may also be used in combination with one or more co-additives
such as known in the art, for example the following: detergents, antioxidants
(to
~o avoid fuel degradation), corrosion inhibitors, dehazers, demulsifiers,
metal
deactivators, antifoaming agents, cetane improvers, cosolvents, package
compatibilisers, and middle distillate cold flow improvers.
15 EXAMPLES
The following examples illustrate the invention. The following materials and
procedures were used and the results are tabulated below.
2o Additives
A. An hydroxy amine of formula
CH2CH20H
C~aHs~N
CH2CH20H
Fuels
I: a middle distillate fuel oil having the following characteristics-
~ sulphur content (wt %) <0.01
~ viscosity at 20°C (cSt) 2.486
~ density at 15°C (Kg/dm3) 0.8136
II: a standard kerosene fuel such as commercially available
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III: a middle distillate fuel oil having the following characteristics-
~ sulphur content (wt %) 0.18
~ viscosity at 20°C (cSt) 4.904
~ density at 15°C (Kg/dm3) 0.8462
Example 1
The Additive A was dissolved in the fuels I and II at various concentrations
and
~o the resulting compositions tested using the High Frequency Reciprocating
Rig (or
HFRR) test described in D. Wei and H. Spikes, Wear, Vol. 111, No. 2, p. 217,
1986; and R. Caprotti, C. Bovington, W. Fowler and M. Taylor, SAE paper
922183. SAE fuels and tubes meeting Oct. 1992, San Francisco, USA.
This test is known to provide a measure of the lubricity of a fuel.
HFRR Test
The results are expressed as wear scar diameter. Additionally the coefficient
of
2o friction was measured. Tests were done at different temperatures as
indicated.
The concentration of additive used is shown in the table below.
Additive A Coefficient Wear
of Scar
Concentration (ppm,Friction Diameter
mm
wei htlwei ht) 20C 60C 20C 60C
Fuell Nil 0.48 0.55 0.58 0.67
50 0.37 0.38 0.52 0.60
100 0.24 0.32 0.38 0.58
500 0.22 0.22 0.31 0.42
Fuelll Nil 0.34 0.35 0.59 0.77
50 0.32 0.32 0.53 0.52
100 0.26 0.26 0.35 0.50
500 0.24 0.24 0.34 0.45
These results show improved lubricity using Additive A.
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Example 2
Additive A was added to fuel oil III at various concentrations and the
antifoam
pertormance was measured at 0°C. The test used was as follows:
Each sample was agitated vigorously for a period and the time, in seconds, for
the
foam to collapse was then observed. The results of the untreated and treated
fuels are compared in the table below.
Additive A ConcentrationFoam Collapse Time (sec)
(ppm, weightlweight) (Average of 2 readings)
Fuel III 0 83.5
5 40
50 35
500 15.5
These results show a marked reduction in the tendency of the fuel to foam when
Additive A is present.
