Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO 94/17160 ~15 ~ 3 4 ~ PCT/EP94/00148
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Fuel Composition
This invention relates to fuel compositions useful, for example, to improve
lubricity and reduce wear in diesel engines.
The art describes esters as additives for diesel engine fuel. For example,
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 combinationsincluding, for example, glycerol monoesters and glycerol diesters as diesel fuel10 additives, the combinations being described as leading to advantages including
less wear of the fuel-injection equipment, piston rings and cylinder liners.
GB-A-1,50~,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
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 onthe weight of the fuel.
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 sùlphur 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
25 content in diesel fuel will be 0.05% by weight. Complete conversion to the 0.05%
maximum may be required during 1996.
The process for preparing low sulphur content fuels, in addition to reducing
sulphur content, also reduces the content of other components of the fuel such as
30 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, eg. in high
35 pressure fuel injection systems such as high pressure rotary distributors, in-line
pumps and unit injectors and injectors. Such severe failures are due to wear that
CONFIRMATION COPY
WO 94/17160 PCT/EP94/00148
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is completely different from the corrosive wear problem described in
GB-A-1,505,302.
As stated, such failure can occur early in the life of an engine; in contrast, the
5 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 lubes. 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.
Thus, a first aspect of the invention is a fuel oil composition comprising a major
proportion of a liquid hydrocarbon middle distillate fuel oil having a sulphur
concentration of 0.2% by weight or less, and a minor proportion of an additive
comprising an ester of a carboxylic acid and an alcohol wherein the acid has from
2 to 50 carbon atoms and the alcohol has one or more carbon atoms.
A second aspect of the invention is the use of a fuel oil 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.
The examples of this specification will demonstrate the efficacy of the additives of
the invention in reducing wear when fuel oils of the invention are used.
Whilst not wishing to be bound by any theory, it is believed that of the additive, in
35 use of the composition in à compression-ignition internal combustion engine, is
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
wo 94/17160 215 ~ 3 ~ q PCTIEP94/00148
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
r reduction in friction, or an increase in electrical contact resistance in any test
5 where two or more loaded bodies are in relative motion under non-hydrodynamic
lubricating conditions.
The features of the invention will now be described in further detail.
1 o ADDITIVE
As stated, it is believed that the additive, which may be a single additive or
mixture of additives, 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 surface
can be demonstrated by, for example, measuring electrical contact resistance or
electrical capacitance.
Examples of tests 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
according to this invention are the Ball On Cylinder Lubricant Evaluator and High
Frequency Reciprocating Rig tests which will be referred to hereinafter.
The acid, alcohol and ester will now be discussed in further detail as follows.
(i) Acid
The acid from which the ester is derived may be a mono or polycarboxylic
acid such as aliphatic, saturated or unsaturated, straight or branched
chain, mono and dicarboxylic acids being preferred. For example, the acid
may be generalised in the formula
R'(COOH)x
WO 94/17160 2 ~ ~ ~ 3 ~ ~ PCT/EP94/00148
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where x represents an integer and is 1 or more such as 1 to 4, and R'
represents a hydrocarbyl group having from 2 to 50 carbon atoms and
which is mono or polyvalent corresponding to the value of x, the -COOH
groups, when more than one is present, optionally being substituent on
different carbon atoms from one another.
'Hydrocarbyl' means a group containing carbon and hydrogen which group
is connected to the rest of the molecule via a carbon atom. It may be
straight or branched chain which chain may be interrupted by one or more
hetero atoms such as O, S, N or P, may be saturated or unsaturated, may
be aliphatic or alicyclic or aromatic including heterocyclic, or may be
substituted or unsubstituted. Preferably, when the acid is monocarboxylic,
the hydrocarbyl group is an alkyl group or an alkenyl group having 10 (e.g.
12) to 30 carbon atoms, i.e. the acid is saturated or unsaturated. The
alkenyl group may have one or more double bonds, such as 1, 2 or 3.
Examples of saturated carboxylic acids are those with 10 to 22 carbon
atoms such as capric. Iauric, myristic, palmitic, and behenic acids and
examples of unsaturated carboxylic acids are those with 10 to 22 carbon
atoms such as oleic, elaidic, palmitoleic, petroselic, riconoleic, eleostearic,
linoleic, linolenic, eicosanoic, galoleic, erucic and hypogeic acids. When
the acid is polycarboxylic, having for example from 2 to 4 carboxy groups,
the hydrocarbyl group is preferably a substituted or unsubstituted
polymethylene.
25 (ii) Alcohol
The alcohol from which the ester is derived may be a mono or polyhydroxy
alcohol such as a trihydroxy alcohol. For example, the alcohol may be
generalised in the formula
R2(0H)y
where y represents an integer and is 1 or more and R2 represents a
hydrocarbyl group having 1 or more carbon atoms such as up to 10 carbon
atoms, and which is mono or polyvalent corresponding to the value of y,
the -OH groups, when more than one is present, optionally being
substituent on different carbon atoms from one another.
._ wo 94/17160 215 ~ 3 ~ 4 PCT/E~94100148
'Hydrocarbyl' has the same meaning as given above for the acid. For the
alcohol, the hydrocarbyl group is preferably an alkyl group or a substituted
or unsubstituted polymethylene group. Examples of monohydric alcohols
are lower alkyl alcohols having from 1 to 6 carbon atoms such as methyl,
ethyl, propyl and butyl alcohols.
Examples of polyhydric alcohols are aliphatic, saturated or unsaturated,
straight chain or branched alcohols having 2 to 10, preferably 2 to 6, more
preferably 2 to 4, hydroxy groups, and having 2 to 90, preferably 2 to 30,
more preferably 2 to 12, most preferably 2 to 5, carbon atoms in the
molecule. As more particular examples the polyhydric alcohol may be a
glycol or diol, or a trihydric alcohol such as glycerol.
(iii) The Esters
The esters may be used alone or as mixtures of one ore more esters and
may be composed only of carbon, hydrogen and oxygen. Preferably the
ester has a molecular weight of 200 or greater, or has at least 10 carbon
atoms, or has both.
Examples of esters that may be used are lower alkyl esters, such as
methyl esters, of the above exemplified saturated or unsaturated
monocarboxylic acids. Such esters may, for example, be obtained by
saponification and esterification of natural fats and oils of plant or animal
origin or by their transesterification with lower aliphatic alcohols.
Examples of esters of polyhydric alcohols that may be used are those
where all of the hydroxy groups are esterified, those where not all of the
hydroxy groups are esterified, and mixtures thereof. Specific examples
are esters prepared from trihydric alcohols and one or more of the above-
mentioned saturated or unsaturated carboxylic acids, such as glycerol
monoesters and glycerol diesters, e.g. glycerol monooleate, glycerol
dioleate and glycerol monostearate. Such polyhydric esters may be
- prepared by esterification as described in the art and/or may be
commercially availàble.
The ester may have one or more free hydroxy groups.
WO 94/17160 PCT/EP94/00148
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FUEL OIL
Preferably, the sulphur concentration is 0.05% by weight or less, such as 0.01%
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 for reducing the sulphur
concentration of hydrocarbon distillate fuels, such methods including for example
solvent extraction, sulphuric acid treatment, and hydrodesulphurisation.
By "tricyclic aromatic" is meant a fixed system where three aromatic rings are
fused together. Preferably, the fuel contains less than 1% by weight of such a
component.
Examples of "polar components" are compounds such as those containing O, S
or N; and esters; and alcohols.
The above-mentioned wear problem is found to become progressively more
acute as the polar component concentration of the fuel is decreased; for
example, it may be particularly severe at concentrations below 250 ppm, such as
below 200 ppm and specifically in fuels having polar component concentrations of170 ppm and 130 ppm respectively. Such polar component concentrations may
conveniently be measured by High Pressure Liquid Chromatography, sometimes
referred to as HPLC.
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
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.
The concentration of the additive of the invention in the fuel oil may be up to
250,000 ppm, for example up to 10,000 ppm such as 1 to below 1000 ppm
_ WO 94/17160 215 4 3 4 4 PCT/EP94/00148
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(active ingredient) by weight per weight of fuel, preferably 10 to 500 ppm, morepreferably 10 to 200 ppm.
The additive may be incorporated into bulk fuel oil by methods known in the art.5 Conveniently, the additive may be so incorporated in the form of a concentratecomprising 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%,
most preferably 10 to 50 wt% of the additive, preferably in solution in the oil.10 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;
and alkoxyalkanols such as 2-butoxyethanol. The carrier liquid must of course beselected having regard to its compatibility with the additive and with the fuel.
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-
20 additives such as known in the art, for example the following: detergents,antioxidants (to avoid fuel degradation), corrosion inhibitors, dehazers,
demulsifiers, metal deactivators, antifoaming agents, cetane improvers,
cosolvents, package compatibilisers, and middle distillate cold flow improvers.
25 EXAMPLES
The following examples illustrate the invention. The following materials and
procedures were used and the results were as follows.
30 Additives
D: Glycerol monooleate.
- E: Di-isodecyl adipate.
WO 94/17160 215 4 3 4 4 PCT/EP94/00148
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Fuels
The fuels used, designated I and ll, were diesel fuels having the following
characteristics
S content <0.01 % (wt/wt)
Aromatics content <1 % (wt/wt)
Cetane number 55.2 to 56.1
Cold Filter Plugging Point Temperature (CFPPT) -36 C
0 95% boiling point 273 C
Il S content <0.01% (wt/wt)
Aromatics not measured
Cetane number not measured
CFPPT -41-C
95% boiling point 263 C
Tests
Certain of Additives D and E were dissolved in certain of fuels I and ll and theresulting composition tested using:
o the Ball On Cylinder Lubricant Evaluator (or BOCLE) test described in
Friction and wear devices, 2nd Ed., p. 280, American Society of Lubrication
Engineers, Park Ridge lll. USA; and F. Tao and J. Appledorn, ASLE trans.,
11, 345-352 (1968); and
o 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
lubes. meeting Oct. 1992; San Francisco, USA.
Both tests are known to provide a measure of the lubricity of a fuel.
WO 94/17160 2 15 4 3 4 ~ PCTIEP94/00148
Resu Its
The tables below give the results.
5 (A) BOCLETest
The results are given as the wear scar diameter. A lower value therefore
indicates less wear than a higher value. All tests were done at ambient
temperature.
0
Fuel I
AdditiveAdditive Concentration Result
(ppm; wVwt) (IJm)
Base Fuel - 852
D 200 505
Fuel ll
AdditiveAdditive Concentration Result
(wt%) (~m)
Base Fuel - 700
D 50 570
D 100 500
D 200 520
D 500 480
D 1,000 430
(B) HFRR Test
The results are also expressed as wear scar diameter. Additionally,
coefficient of friction was measured. Tests were done at different
temperatures as indicated. In Fuel 1, Additive D's concentration was
200 ppm (wt/wt) and Additive E's concentration was 10,000 ppm. In Fuel
Il, Additive D's concentration is indicated in parentheses.
WO 94/17160 215 4 3 ~ !I PCT/EP94/00148
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Fuel I
20 C 25 C 60 C
Wear Wear Wear
AddjtjVe Coemcient Scar Scar Co~rr,~e"t Scar
of FrictionDiameter Diameter of Friction Diameter
(~m) (lJm) (~m)
Base 0.59 540 576 0.72 590
D 0.19 240 180 0.19 160
E 344 442
Fuel ll
20 C 60 C
Wear Scar Wear Scar
Additive Ceffi.lCient Diameter Coeffclent Djameter
of Fnctlon (l~m) f Friction (l~m)
Base Fuel 0.60 600 0.75 630
D (10 ppm) 0.95 530 0.83 570
D (50 ppm) 0.55 580 0.58 590
D (100 ppm) 0.41 530 0.39 560
D (150 ppm) 0.21 o 0.22 240
D (200 ppm) 0.23 <20 0.23 250
D (1000 ppm) 0.22 o 0.23 250
The results show that lubricity is improved by using additives D and E.
