Note: Descriptions are shown in the official language in which they were submitted.
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GASOLINE COMPOSITION
This invention relates to low sulphur gasoline compositions which have
improved
response to friction reducing additives.
Fuels such as gasolines and diesels are used rather widely in automotive
transport
and for providing power for heavy duty equipment, especially diesels due to
their high fuel
economy. However, one of the problems when such fuels are burned in internal
combustion
engines is their low lubricity. This reduction in lubricity arises because as
the sulphur
content in the fuel is reduced eg by hydrodesulphurisation, this process also
incidentally
removes the lubricity providing polar or friction reducing molecules such as
eg the
nitrogenous compounds present in such fuels. A prior published SAE Paper No.
962010 by
Wei Dan Ping et al entitled "Comparison of the Lubricity of Gasoline and
Diesel Fuels"
(1996) describes the effects of various additives on such fuels including low
sulphur fuels.
Whilst efforts hitherto have been devoted to the addition of such friction
reducing
nitrogenous compounds into the fuels after hydrodesulphurisation to restore
the lubricity of
the fuel, little attention has been paid to the nature of the fuel itself in
order to improve the
efficiency of such fuels.
Prior published GB-A-2306246 and GB-A-2307247 relate to the use of carboxylic
acid derivatives as an additive for improving the lubricity of low sulphur-
content fuels which
are primarily middle distillate fuels such as eg diesel, jet and biodiesel
fuels. However,
there is no mention of gasolines or fuels having a sulphur content of less
than 30 ppm in
these documents.
Similarly, EP-A-0860494, EP-A-0739970 and EP-A-0635558 relate to low sulphur
diesel, gas oils and gas oils (diesel fuels) respectively containing esters
derived by
transesterification of vegetable oils, glycerol/fatty acid esters and lower
alkyl esters of a
mixture of saturated and unsaturated fatty acids derived from oleaginous seeds
respectively
as a lubricity improving agent. In each case there is no mention of low
sulphur gasolines,
especially gasolines having a sulphur content of < 30 ppm.
W099/00467 describes a fuel composition of improved lubricity comprising a
spark
ignition fuel and an alkanolamide of a fatty acid or a modified fatty acid
having a maximum
sulphur content of 0.05% based on mass. However, no gasolines are mentioned
and all of
the examples relate to diesels, especially Swedish Class I low sulphur diesel
fuel. There is
also no reference to the bromine number or IJV absorbance of the fuels tested
or claimed.
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It has now been found that the efficacy of the friction reducing additives can
be
significantly improved by mixing the same with fuels of specific,
predetermined
characteristics.
Accordingly, the present invention is a composition comprising (i) a low
sulphur
gasoline having a sulphur content of less than 30 ppm, a bromine number of
less than about
and an ultraviolet absorbance at 319 nm below 0.15 and (ii) an effective
amount of an
ashless friction reducing additive which is a fatty acid having 10-30 carbon
atoms or a
derivative thereof.
The gasoline should have a bromine number (which is related to the amount of
olefins in the fuel) below 10, suitably below 5 and preferably below 4.5.
Furthermore, the
gasoline should have a sulphur content below 30 ppm, suitably below 20 ppm and
preferably
below 10 ppm. Again the LJV absorbance of the fuel at 319 nm should be below
0.1,
suitably below 0.07 and preferably below 0.05.
The ashless friction reducing additive in the composition is suitably a liquid
at room
temperature and pressure and is selected from C10-C30 fatty acids, preferably
a C10-C24
fatty acid, or a derivative thereof and mixtures thereof. Such ashless
friction reducing
additives are suitably derived from naturally occurnng fats and oils and the
preferred
derivatives are suitably selected from the alkylamine salts, alkyl amides and
alkyl esters of
such acids and oligomers thereof. An example of an alkyl amine carboxylate
salt is n-
butylamine oleate or a derivative thereof and an example of a naturally
occurring fatty acid
is a substance comprising a fatty acid, a tall oil fatty acid or derivatives
thereof.
n-Butylamine oleate has the formula:
CH3-(CHZ)7-CH:CH-(CHZ)7-C(O)O- +IVH3C4H9
One such n-butylamine oleate is commercially sold as a friction modifier as RS
124 by Bitrez
Ltd.
The substance comprising fatty acids may be either 100% fatty acids, or
substantially
100% fatty acids, or may be a mixture of fatty acids and/or tall oil acids or
derivatives
thereof. Such a mixture suitably contains at least 30% w/w, preferably at
least 50% w/w of
fatty acids. An example of a suitable commercially available substance
containing fatty acids
is TOLAD~ 9103 (ex Baker-Petrolite Ltd).
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The friction reducing additive is used in an amount sufficient to provide
effective
lubricity to the composition. The friction reducing additive is suitably used
in an amount of
less than 1000 mg per kilogram of base fuel in the composition, preferably
from 1 to 500 mg
and more preferably from about 5 to 100 mg per kg of base fuel in the
composition. It has
been found that a gasoline with these characteristics is much more responsive
to the amount
of the ashless friction reducing agent specified above added than conventional
fuels which
do not possess these characteristics. A typical example of such a gasoline is
the so called
"Rotterdam gasoline" which suitably has a final boiling point below
200°C, preferably about
185°C. The ashless friction reducing additive may be part of an
additive concentrate
comprising a number of additives. In the additive concentrate, the amount of
the friction
reducing additive is suitably from 0.2-25% w/w, preferably from 0.5-20% w/w
and more
preferably from 3 to 15% w/w. On the basis of the total concentrate, the treat
level of the
friction reducing additive in the gasoline is suitably from 4-200 ppm,
preferably from 10-100
ppm and more preferably from 25-75 ppm.
The present invention is further illustrated with reference to the following
Examples
and comparative tests:
EXAMPLES:
The following fuels with varying degrees of bromine numbers, sulphur content
and
UV absorbance at 319 nm were tested for their responsiveness to a lubricity
additive. Of
these, both the Rotterdam and the Neste 95UL base gasolines show comparable
sulphur
contents, yet the Rotterdam fuel (which has a final boiling point of
186.2°C) is more
responsive to lubricity additive. This responsiveness, as measured by the
percentage
reduction in friction relative to base fuel (Table 2) is linked to the fuel's
substantially lower
bromine number and UV absorption at 319 nm. (Table 1 ) (Note: the measure of
UV
absorbance and bromine number are both dimensionless quantities).
TABLE 1
FUEL & SOURCE BROMINE NO. % SULPHUR BY WT UVA 319 nm)
Fawle (A)* 37.72 0.04 0.398
Neste 95UL* 21.7 0.0027 0.323
Rotterdam 4.17 0.0028 0.038
Fawley (B)* 16.11 0.01 0.172
Fawle (C)* 13.28 0.02 0.567
*Indicates a test fuel not according to the invention.
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The above fuels were tested at various treat rates to determine the change in
coefficient of friction and the mean friction values and the results are
tabulated in Tables 2
and 3 below:
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TABLE 2
Base Fuel Additive Treat Rate Mean FC OFC %~FC
mUl 000 litres
Fawley (A) None 0 0.224
Fawley (B) n-BAO 12.5 0.154 0.071 31.5
Fawley (C) Tolad~ 9103 12.5 0.145 0.079 35.3
Neste 95 UL None 0 0.225
Neste 95 UL n-BAO 12.5 0.152 0.073 32.5
Neste 95 UL Tolad~ 9103 12.5 0.153 0.072 32.1
Rotterdam# None 0 0.439
Rotterdam# n-BAO 12.5 0.157 0.283 64.4
Rotterdam# Tolad~ 9103 12.5 0.152 0.287 65.5
Fawley (B) None 0 0.304
Fawley (B) n-BAO 12.5 0.158 0.146 47.9
Fawle (B) Tolad~ 9103 12.5 0.214 0.090 29.7
Fawley (C) None 0* 0.315
Fawle (C) n-BAO 12.5* 0.204 0.111 35.2
Fawley (C) Tolad~ 9103 12.5* 0.218 0.097 30.8
Mean FC= mean friction coefficient
S AFC= Mean FC (base fuel)- Mean FC (additised fuel)
%OFC= [Mean FC (base fuel)- Mean FC (additised fuel)] x 100/ Mean FC (base
fuel)
*These are by weight ie mg/Kg
#Fuels according to the invention.
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TABLE 3
~ Base Fuel Additive Treat Mean Friction% Friction
Rate Coefficient Coefficient
m /K
Fawley (C) None 0 0.315
Fawley (C) n-BAO 12.5 0.204 35.2
Fawley (C) n-BAO 25 0.146 53.6
Fawley (C) n-BAO 50 0.132 58.1
Fawley (C) n-BAO 100 0.118 62.5
Fawley (C) None 0 0.315
Fawley (C) Tolad~ 9103 12.5 0.218 30.8
Fawley (C) Tolad~ 9103 25 0.174 44.8
Fawley (C) Tolad~ 9103 50 0.149 52.7
Fawley (C) Tolad~ 9103 100 0.137 56.5
n-BAO - n-butylamine oleate; Tolad~
FC-Friction Coefficient
