FUEL COMPOSITION

COMPOSITION DE CARBURANT

English Abstract

This invention relates to a fuel composition comprising a base fuel having a
final boiling point above 150 ~C and an anti-foam, characterised in that the
anti-foam comprises di-isobutylene in an amount greater than 2.5 % by volume
based on the total fuel composition. The addition of this anti-foam reduces
the break-up time for any foam formed significantly.

French Abstract

L'invention concerne une composition de carburant comprenant un carburant de base à point final supérieur à 150 ·C et un agent antimousse qui renferme du di-isobutylène selon une quantité supérieure à 2,5 %, en volume, par rapport à la composition totale. L'adjonction de l'agent antimousse réduit le temps de rupture propre à toute formation appréciable de mousse.

Claims

4~~
Claims:
1. A fuel composition comprising a base fuel having a final boiling point
greater than
150°C and an anti-foam, characterised in that the anti-foam comprises
di-isobutylene
in an amount greater than 2.5 % by volume based on the total fuel composition.
2. A composition according to Claim 1 wherein the base fuels comprises
mixtures of
saturated, olefinic and aromatic hydrocarbons derivable from straight run
streams,
thermally or catalytically cracked hydrocarbon feedstocks, hydrocracked
petroleum
fractions, catalytically reformed hydrocarbons, or synthetically produced
hydrocarbon mixtures.
3. A composition according to Claim 1 or 2 wherein the base fuel is a
petroleum fuels
having a boiling range from gasoline (which typically boils in the range from
50 and
200°C with a final boiling point > 150°C ) to distillate fuel
(which typically boils
between 150 and 400°C).
4. A composition according to any one of the preceding Claims wherein the base
fuel is
a common distillate fuel selected from motor gasoline, kerosene and diesel
fuels.
5. A composition according to any one of the preceding Claims wherein the base
fuel
has a sulphur content of less than 100 ppm by weight.
6. A composition according to any one of the preceding Claims wherein the base
fuel
has a sulphur content of less than 50 ppm by weight.
7. A composition according to any one of the preceding Claims wherein the di-
isobutylene comprises a mixture of 2,4,4-trimethylpent-1-ene and 2,4,4-
trimethylpent-2-ene.
8. A composition according to any one of the preceding Claims wherein the di-
isobutylene comprises a mixture of 2,4,4-trimethylpent-1-ene and 2,4,4-
trimethylpent-2-ene in a ratio of 75% to 25% by weight.
9. A composition according to any one of the preceding Claims wherein di-
isobutylene
is used in an amount from 2.5 - 35 % by volume.

10. A composition according to any one of the preceding Claims wherein di-
isobutylene
is used in an amount from 5 to less than 15% by volume of the total fuel
composition.

Description

CA 02397456 2002-07-12
WO 01/60955 PCT/USO1/09792
FUEL COMPOSITION
This invention relates to fuel compositions comprising an anti-foam additive
to
reduce the time needed to break up any foam formation during the filling of a
vehicle's fuel
tank thereby enabling a more complete filling of the tank and at the same time
reducing risk
of spillage.
The problem of foaming of fuels due to entrainment of air during filling of
fuel tanks
of vehicles is well known. The problem has hitherto been mitigated by adding
to the fuel
antifoams which are substantially non-hydrocarbonaceous. An example of such a
non-
hydrocarbonaceous additive is a silicon containing polymer. Non-
hydrocarbonaceous
additives usually have to undergo a rigorous testing programme with respect to
their
compatibility with the fuel and also environmental considerations. However, if
the additive
is a hydrocarbon, especially a non-aromatic hydrocarbon, the issues of
compatibility and
environmental considerations are not as critical. JP-A-08073870 discloses
gasoline
compositions for two-cycle engines which contain at least 10 vol % 7-8C
olefinic
hydrocarbons and have a TSO of 93-105°C, a final distillation
temperature of 110-150°C and
an octane No. by the motor method of at least 95. Amongst the 11 olefins
listed is
mentioned 2,4,4-trimethyl-1-pentene. However, it is not clear whether these
olefins are used
as a blend of several. In any event, the olefins are not used as anti-foaming
agents but to
achieve high output and low fuel consumption and to avoid seizure even at high
compression
ratios. Moreover, gasoline used in two-cycle engines (ie two-stroke engines)
inevitably have
lubricating oils admixed therewith and hence are not as susceptible to foaming
as gasolines
free of such lubricating oils.
Similarly, SAE Paper 950740 describes various compounds being added to a
mixture of toluene (boiling point about 110°C) and isooctane (boiling
point 99°C) to
monitor the emissions of vehicles powered therewith. One such compound added
is di-
isobutylene in an amount > 15% by volume. The resultant mixture is unlikely to
have a final
boiling point above 150°C and there is no mention of the use of di-
isobutylene as an anti-
foam in this document.
Similarly, JP-A-06200263 describes a composition which contains at least 65%
by
volume based on the total base fuel of a high boiling component with a boiling
point from
80-120°C which uses 7-8C paraffin type or olefin type hydrocarbon. The
abstract of this
patent makes no mention of any other base fuels or specific olefins in this
range and there is
no mention of any of such olefins as anti-foaming agents.

CA 02397456 2002-07-12
WO 01/60955 PCT/USO1/09792
2
Again WO 99/49003 discloses gasoline formulations which contain inter alia at
least
5% volume of saturated C~/Cg branched chain hydrocarbons. In any event, there
is no
mention of the use of these as anti-foaming agents.
It is an object of the present invention to formulate a fuel compositions
comprising an
anti-foam which is an unsaturated, non-aromatic hydrocarbon capable of
reducing the break-
up time to disperse such any foams formed.
Accordingly, the present invention is a fuel composition comprising a base
fuel
having a final boiling point greater than 150°C and an anti-foam,
characterised in that the
anti-foam comprising di-isobutylene in an amount greater than 2.5 % by volume
based on
the total fuel composition.
The base fuels may comprise mixtures of saturated, olefinic and aromatic
hydrocarbons and these can be derived from straight run streams, thermally or
catalytically
cracked hydrocarbon feedstocks, hydrocracked petroleum fractions,
catalytically reformed
hydrocarbons, or synthetically produced hydrocarbon mixtures. The present
invention is
particularly applicable to a broad range of petroleum fuels from the light
boiling gasoline
(which typically boils between 50 and 200°C) to distillate fuel (which
typically boils
between 150 and 400°C). The most common distillate fuels suitable for
use in the present
invention as base fuels are selected from motor gasoline, kerosene and diesel
fuels. The
sulphur content of the base fuel is suitably less than 100 ppm by weight, is
preferably less
than 50 ppm by weight and more preferably less than 30 ppm by weight. Such low
sulphur
levels can be achieved in a number of ways. For instance, this may be achieved
by well
known methods such as eg, catalytic hydrodesulphurisation.
Di-isobutylene used as an anti-foam in the fuel compositions of the present
invention
is present in said composition in an amount greater than 2.5% by volume,
suitably from
2.5% to 35% by volume, preferably 5.0 % to less than 15% by volume and is more
preferably present in an amount from 7.5 to less than 15% by volume of the
total fuel
composition. Di-isobutylene can readily be obtained by dimerisation of
isobutylene. It is
generally prepared from a crude mixture of olefins and usually comprises a
mixture of
various C8-olefin isomers but always comprises 2,4,4-trimethylpent-1-ene
admixed with
2,4,4-trimethylpente-2-ene. These two isomers are suitably present in the di-
isobutylene in a
weight ratio of about 75% (-1-ene) to about 25% (-2-ene).
Di-isobutylene has an advantage over other non-hydrocarbonaceous anti-foams
such
as silicon based polymers in that di-isobutylene is substantially miscible
with conventional

CA 02397456 2002-07-12
i~VO 01/60955 PCT/US01/09792
3
fuels in all proportions. Di-isobutylene has the further advantage that
current plants making
methyl tert-butyl ether (hereafter "MTBE") from isobutylene and methanol (MTBE
having
more recently fallen out of favour upon environmental considerations), can be
readily
switched to convert the same isobutylene feedstock to di-isobutylene.
Furthermore, di-
isobutylene can readily make up the additional component volume to replace the
MTBE
used hitherto in automotive fuel component pool.
It has also been found that the reduction in break-up time for foams formed is
not due
to a dilution effect of di-isobutylene. Test results show that addition of up
to 2.5% by
volume of di-isobutylene in the fuel did not show any reduction in the foam
break-up time of
the fuel tested.
The present invention is further illustrated with reference to the following
Examples:
Tests were carned out in which di-isobutylene (a mixture of 3 parts 2,4,4-
trimethylpent-1-ene and 1 part 2,4,4-trimethylpent-2-ene) was added to varying
quantities to
a distillate fuel which was susceptible to foam formation. The resultant
admixture was
tested in the BNPe Anti-Foam test (French Standard Test NF M 07-075) and the
results
obtained are shown in Table 1 below:
TABLE 1
Blend Fuel DIB DIB Foam Mean Break-up Mean
ml ml % Vol Value Time Value
(ml) seconds
1 300 0 0 126 124 125 79.2 82.5 80.9
2 292.5 7.5 2.5 130 128 129 79.7 81 80.4
3 285 15 5 13_0__132 131 62.3 66.9 64.6
4 270 30 10 ~ 142 ~ 140 141 51.9 49.6 50.8
I I
DIB - Di-isobutylene (a mixture of 3 parts 2,4,4-trimethylpent-1-ene and 1
part 2,4,4-
trimethylpent-2-ene)