Note: Descriptions are shown in the official language in which they were submitted.
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Improvements in Fuel Oil Compositions
This invention relates to improvements in fuel oil compositions, and more
especially to
fuel oil compositions containing detergent species and susceptible to wax
formation at low
temperatures.
Fuel oils, whether derived from petroleum or from vegetable sources, contain
components,
e.g., n- alkanes or methyl n-alkanoates, that at low temperature tend to
precipitate as large, plate-
like crystals or spherulites of wax in such a way as to form a gel structure
which causes the fuel
to lose its ability to flow. The lowest temperature at which the fuel will
still flow is known as the
pour point.
As the temperature of a fuel falls and approaches the pour point, difficulties
arise in
transporting the fuel through lines and pumps. Further, the wax crystals tend
to plug fuel lines,
screens, and filters at temperatures above the pour point. These problems are
well recognised in
the art, and various additives have been proposed, many of which are in
commercial use, for
depressing the pour point of fuel oils. Similarly, other additives have been
proposed and are in
commercial use for reducing the size and changing the shape of the wax
crystals that do form.
Smaller size crystals are desirable since they are less likely to clog a
filter. The wax from a diesel
fuel, which is primarily an alkane wax, crystallizes as platelets. Certain
additives inhibit this and
cause the wax to adopt an acicular habit, the resulting needles being more
likely to pass through a
filter, or form a porous layer of crystals on the filter, than are platelets.
Other additives may also
have the effect of retaining the wax crystals in suspension in the fuel,
reducing settling and thus
also assisting in prevention of blockages. These types of additives are often
termed 'wax anti-
settling additives' (WASA) and are commonly polar nitrogen species.
Many additives have been described over the years for enhancing engine
cleanliness, e.g.
for reducing or removing deposits in the intake system (e.g. carburettors,
intake manifold, inlet
valves) or combustion chamber surfaces of spark-ignition engines, or for
reducing or preventing
injector nozzle fouling in compression-ignition engines.
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For example, UK Patent specification No 960,493 describes the incorporation of
metal-
free detergents, in the form of polyolefin-substituted succinimides of
tetraethylene pentamine, in
base fuels for internal combustion engines. The use of such metal-free
detergents is now
widespread. Most commonly used are polyisobutylene substituted succinimides
which are the
reaction products of polyisobutylene substituted acylating agents such as
succinic acid or
anhydride with polyamines. Such materials and their methods of production will
be known to
those skilled in the art.
The trend in modem diesel engine technology is to increase power output and
efficiency
by increasing injection pressures and decreasing injector nozzle diameters.
Under these
conditions, the build up of injector deposits is more likely and the
deposition which occurs is
more severe. This has led fuel manufacturers to produce new types of fuels
which are often sold
as 'premium' grades and promoted as being especially effective to improve
engine cleanliness.
To meet this performance claim, such premium fuels usually contain
significantly higher levels
of detergent than non-premium grade fuels.
Whilst largely effective with regard to engine cleanliness, a drawback has
been identified
with the use of high levels of detergent in fuel oils. Specifically, it has
been observed that the
presence of high levels of polyamine detergent species in premium grade fuels
can interfere with
the cold-flow performance of wax anti-settling additives when these are also
present in the fuel.
So, although the fuel may be satisfactory from an engine cleanliness
viewpoint, its low
temperature properties, in terms of wax anti-settling and cold filter plugging
point (CFPP) may
not be adequate.
The present invention is based on the discovery that the additional presence
of a third co-
additive species can restore the low temperature properties of the fuel
containing a wax anti-
settling additive and a polyamine detergent.
W095/03377 describes that certain fuel additives not known for providing
improvements
in low temperature properties can nevertheless be beneficial to such
properties when combined
with copolymeric ethylene flow improvers. Oil soluble ashless dispersants are
disclosed as one
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such class of fuel additives. Further additives including wax anti-settling
additives may
additionally be incorporated.
EP 0 104 015 A describes that certain carboxylic acids, preferably aromatic
acids such as
benzoic acid, can be used to improve the solubility of certain wax anti-
settling additives when
they are combined together in a fuel additive concentrate. At least one mole
of acid is required
per mole of wax anti-settling additive.
Thus in accordance with a first aspect, the present invention provides a
method of
improving the low temperature properties of a fuel oil composition comprising
a major amount of
a fuel oil and minor amounts of (a) at least one polar nitrogen compound
effective as a wax anti-
settling additive and (b) at least one polyamine detergent, the method
comprising adding to the
composition (c) at least one acidic organic species.
In accordance with a second aspect, the present invention provides the use of
(c) at least
one acidic organic species to improve the low temperature properties of a fuel
oil cotnposition;
wherein the fuel oil composition comprises a major amount of a fuel oil and
minor amounts of (a)
at least one polar nitrogen compound effective as a wax anti-settling additive
and (b) at least one
polyamine detergent.
In accordance with a third aspect, the present invention provides the use of
(c) at least one
acidic organic species to substantially restore a loss in low temperature
properties of' a fuel oil
comprising (a) at least one polar nitrogen compound effective as a wax anti-
settling additive,
such loss being attributable to the presence of (b) at least one polyamine
detergent in the fuel oil.
In accordance with a fourth aspect, the present invention provides a process
of
ameliorating a negative interaction on the low temperature performance of (a)
a polar nitrogen
compound effective as a wax anti-settling additive attributable to its use in
combination with (b)
at least one polyamine detergent, the process comprising:
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(i) determining for a fuel oil composition comprising a major amount of a
ftiel oil and
minor amounts of (a) and (b), the amounts of (a) and (b) such that the low
temperature
properties of the fuel oil composition are inferior to the low temperature
properties of a
fuel oil composition comprising the same amount of (a) in the absence of (b);
and,
(ii) determining an amount of (c) at least one acidic organic species, which
when
added to the fuel oil composition is such that the low temperature properties
of the fuel oil
composition are improved; and,
(iii) manufacturing a fuel oil composition comprising (a), (b) and (c) in the
amounts
determined in (i) and (ii).
The observed loss in wax anti-settling and CFPP performance appears to be
limited to the
use of polyamine detergents in combination with WASA components. It is
noteworthy that a
similar loss in performance is not observed when non-polyamine detergents are
used in
combination with WASA components. The addition of the acidic organic species
mitigates this
loss in performance allowing higher levels of polyamine detergents to be used
together with
WASA species without compromising the low temperature properties of the
additised fixel.
As indicated above, the combined presence in a fuel oil of a polyamine
detergent and a
WASA may lead to a reduction in performance in terms of wax anti-settling
and/or C:FPP. With
regard to the first and second aspects, an improvement in the low temperature
properties can refer
to an improvement in terms of either wax anti-settling performance, an
improvement in CFPP or
preferably an improvement in both properties. The restoration of a loss in low
temperature
properties of the third aspect and the amelioration of a negative interaction
of the fourth aspect
will be understood in the same context.
Thus in the first and second aspects, the invention requires that either or
both, preferably
both, of the wax anti-settling behaviour and the CFPP of the fuel oil is
improved when (c) is
present compared to the situation where (c) is absent. It should be noted that
it is not required that
either property necessarily reaches the level which would be expected without
the presence of (b).
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In the third aspect, the use of (c) should return either or both, preferably
both, of the wax
anti-settling behaviour and the CFPP of the fuel oil to the level which would
be expected without
the presence of (b). The use of the term 'substantially restore' should be
taken to include the
situation where, although the precise numerical value of the property may not
be regained, the
difference is not practically significant. Of course, the situation where the
use of (c) leads to
better low temperature properties than would be expected without the presence
of (b) is also
included in the scope of the third aspect.
The fourth aspect should be taken in the same context as the first and second
aspects. That
is, it is not required that either the wax anti-settling performance or the
CFPP of the fuel oil
composition manufactured in step (iii) necessarily reaches the level which
would be expected
without the presence of (b), but simply that at least one property, preferably
both, are improved
relative to those determined in step (i).
The various features of the invention, which are applicable to all aspects,
will now be
described in more detail.
(a) The polar nitrogen compound effective as a wax anti-settlinQ additive.
Such species are known in the art.
Preferred are oil-soluble polar nitrogen compounds carrying one or more,
preferably two
or more, substituents of the formula >NR13, where R13 represents a hydrocarbyl
group containing
8 to 40 atoms, which substituent or one or more of which substituents may be
in the form of a
cation derived therefrom. The oil soluble polar nitrogen compound is generally
one capable of
acting as a wax crystal growth inhibitor in fuels. It comprises for example
one or more of the
following compounds:
An amine salt and/or amide formed by reacting at least one molar proportion of
a
hydrocarbyl-substituted amine with a molar proportion of a hydrocarbyl acid
having from 1 to 4
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carboxylic acid groups or its anhydride, the substituent(s) of formula >NR13
being of the formula
-NR13R14 where R13 is defined as above and R14 represents hydrogen or R13,
providecl that R",
and R14 may be the same or different, said substituents constituting part of
the amine salt and/or
amide groups of the compound.
Ester/amides may be used, containing 30 to 300, preferably 50 to 150, total
carbon atoms.
These nitrogen compounds are described in US Patent No. 4,211,534. Suitable
amines are
predominantly C12 to C40 primary, secondary, tertiary or quaternary amines or
mixtures thereof
but shorter chain amines may be used provided the resulting nitrogen compound
is oil soluble,
normally containing about 30 to 300 total carbon atoms. The nitrogen compound
preferably
contains at least one straight chain C8 to C40, preferably C14 to C24, alkyl
segment.
Suitable amines include primary, secondary, tertiary or quaternary, but are
preferably
secondary. Tertiary and quaternary amines only form amine salts. Examples of
amines include
tetradecylamine, cocoamine, and hydrogenated tallow amine. Examples of
secondary amines
include di-octadecylamine, di-cocoamine, di-hydrogenated tallow amine and
methylbehenyl
amine. Amine mixtures are also suitable such as those derived from natural
materials. A
preferred amine is a secondary hydrogenated tallow amine, the alkyl groups of
which are derived
from hydrogenated tallow fat composed of approximately 4% C14, 31% C16, and
59% C18.
Examples of suitable carboxylic acids and their anhydrides for preparing the
nitrogen
compounds include ethylenediamine tetraacetic acid, and carboxylic acids based
on cyclic
skeletons, e.g., cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-
dicarboxylic acid,
cyclopentane- 1,2-dicarboxylic acid and naphthalene dicarboxylic acid, and 1,4-
dicarboxylic acids
including dialkyl spirobislactones. Generally, these acids have about 5 to 13
carbon atoms in the
cyclic moiety. Preferred acids useful in the present invention are benzene
dicarboxylic acids, e.g.
phthalic acid, isophthalic acid, and terephthalic acid. Phthalic acid and its
anhydride are
particularly preferred. The particularly preferred compound is the amide-amine
salt formed by
reacting 1 molar portion of phthalic anhydride with 2 molar portions of
dihydrogenated tallow
amine.
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Other examples are long chain alkyl or alkylene substituted dicarboxylic acid
derivatives
such as amine salts of monoamides of substituted succinic acids, examples of
which are known in
the art and described in US Patent No. 4,147,520, for example. Suitable amines
may be those
described above.
Other examples are condensates, for example, those described in EP-A-327423.
Other examples of polar nitrogen compounds are compounds containing a ring
system
carrying at least two substituents of the general formula below on the ring
system
-A-NR1sR-6
where A is a linear or branched chain aliphatic hydrocarbylene group
optionally interrupted by
one or more hetero atoms, and R15 and R16 are the same or different and each
is independently a
hydrocarbyl group containing 9 to 40 atoms optionally interrupted by one or
more hetero atoms,
the substituents being the same or different and the compound optionally being
in the form of a
salt thereof. Advantageously, A has from 1 to 20 carbon atoms and is
preferably a methylene or
polymethylene group. Such compounds are described in WO 93/04148 and
W09407842.
Other examples are the free amines themselves as these are also capable of
acting as wax
crystal growth inhibitors in fuels. Suitable amines including primary,
secondary, tertiary or
quaternary, but are preferably secondary. Examples of amines include
tetradecylamine,
cocoamine, and hydrogenated tallow amine. Examples of secondary amines include
di-
octadecylamine, di-cocoamine, di-hydrogenated tallow amine and methylbehenyl
amine. Amine
mixtures are also suitable such as those derived from natural materials. A
preferred amine is a
secondary hydrogenated tallow amine, the alkyl groups of which are derived
from hydrogenated
tallow fat composed of approximately 4% C14, 31% C16, and 59% C18.
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(b) The polyamine detergent.
A preferred class of polyamine detergents are those made by reacting an
acylating agent
having a hydrocarbyl substituent of at least 10 carbon atoms and a nitrogen
compound
characterized by the presence of at least one -NH- group. Typically, the
acylating agent will be a
mono- or polycarboxylic acid (or reactive equivalent thereof) such as a
substituted succinic or
propionic acid and the amino compound will be a polyamine or mixture of
polyamines, most
typically, a mixture of ethylene polyamines. The amine also may be a
hydroxyalkyl-substituted
polyamine. The hydrocarbyl substituent in such acylating agents preferably
averages at least
about 30 or 50 and up to about 200 carbon atoms.
Illustrative of hydrocarbyl substituent groups containing at least 10 carbon
atoms are n-
decyl, n-dodecyl, tetrapropenyl, n-octadecyl, oleyl, chlorooctadecyl,
triicontanyl, etc. Generally,
the hydrocarbyl substituents are made from homo- or interpolymers (e.g.
copolymers,
terpolymers) of mono- and di-olefins having 2 to 10 carbon atoms, such as
ethylene, propylene,
1-butene, isobutene, butadiene, isoprene, 1-hexene, 1-octene, etc. Typically,
these olefins are 1-
monoolefins. This substituent can also be derived from the halogenated (e.g.
chlorinated or
brominated) analogs of such homo-or interpolymers.
The hydrocarbyl substituents are predominantly saturated. The hydrocarbyl
substituents
are also predominantly aliphatic in nature, that is, they contain no more than
one non-aliphatic
moiety (cycloalkyl, cycloalkenyl or aromatic) group of 6 or less carbon atoms
for every 10
carbon atoms in the substituent. Usually, however, the substituents contain no
more than one
such non-aliphatic group for every 50 carbon atoms, and in many cases, they
contain no such
non-aliphatic groups at all; that is, the typically substituents are purely
aliphatic. Typically, these
purely aliphatic substituents are alkyl or alkenyl groups.
A preferred source of the substituents are poly(isobutene)s obtained by
polymerization of
a C4 refinery stream having a butene content of 35 to 75 weight per cent and
isobutene content of
30 to 60 weight per cent in the presence of a Lewis acid catalyst such as
aluminum trichloride or
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boron trifluoride. These polybutenes predominantly contain monomer repeating
units of the
configuration -C(CH3)2CH2-.
The hydrocarbyl substituent is attached to the succinic acid moiety or
derivative thereof
via conventional means, for example the reaction between maleic anhydride and
an unsaturated
substituent precursor such as a polyalkene, as described for example in EP-B-0
451 380.
One procedure for preparing the substituted succinic acylating agents involves
first
chlorinating the polyalkene until there is an average of at least about one
chloro group for each
molecule of polyalkene. Chlorination involves merely contacting the polyalkene
with chlorine
gas until the desired amount of chlorine is incorporated into the chlorinated
polyalkene.
Chlorination is generally carried out at a temperature of about 75 C to about
125 C. If desired, a
diluent can be used in the chlorination procedure. Suitable diluents for this
purpose include poly-
and perchlorinated and/or fluorinated alkanes and benzenes.
The second step in the procedure is to react the chlorinated polyalkene with
the maleic
reactant at a temperature usually within the range of about 100 C to about 200
C. The mole ratio
of chlorinated polyalkene to maleic reactant is usually about 1:1. However, a
stoichiometric
excess of maleic reactant can be used, for example, a mole ratio of 1:2. If an
average of more
than about one chloro group per molecule of polyalkene is introduced during
the chlorination step,
then more than one mole of maleic reactant can react per molecule of
chlorinated polyalkene. It
is normally desirable to provide an excess of maleic reactant; for example, an
excess of about 5%
to about 50%, for example 25% by weight. Unreacted excess maleic reactant may
be stripped
from the reaction product, usually under vacuum.
Another procedure for preparing substituted succinic acid acylating agents
utilizes a
process described in U.S. Pat. No. 3,912,764 and U.K. Pat. No. 1,440,219.
According to that
process, the polyalkene and the maleic reactant are first reacted by heating
them together in a
direct alkylation procedure. When the direct alkylation step is completed,
chlorine is introduced
into the reaction mixture to promote reaction of the remaining unreacted
maleic reactants.
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According to the patents, 0.3 to 2 or more moles of maleic anhydride are used
in the reaction for
each mole of polyalkene. The direct alkylation step is conducted at
temperatures to 180 C to
250 C. During the chlorine-introducing stage, a temperature of 160 C to 225 C
is employed.
The attachment of the hydrocarbyl substituent to the succinic moiety may
alternatively be
achieved via the thermally-driven 'ene' reaction, in the absence of chlorine.
Use af such a
material a the acylating agent leads to products having particular advantages;
for example,
chlorine-free products having excellent detergency and lubricity properties.
In such products, the
reactant is preferably formed from a polyalkene having at least 30% preferably
50% or rr-ore such
as 75% of residual unsaturation in the form of terminal, e.g. vinylidene,
double bonds.
Suitable polyamines are those comprising amino nitrogens linked by alkylene
bridges,
which amino nitrogens may be primary, secondary and/or tertiary in nature. The
polyamines may
be straight chain, wherein all the amino groups will be primary or secondary
groups, or may
contain cyclic or branched regions or both, in which case tertiary amino
groups may also be
present. The alkylene groups are preferably ethylene or propylene groups, with
ethylene being
preferred. Such materials may be prepared from the polymerization of lower
alkylene diamines
such as ethylene diamine, a mixture of polyamines being obtained, or via the
reaction of
dichloroethane and ammonia.
Specific examples of the polyalkylene polyamines (1) are ethylene diamine,
tetra(ethylene)pentamine, tri-(trimethylene)tetramine, and 1,2-propylene
diamine. Specific
examples of hydroxyalkyl-substituted polyamines include N-(2-hydroxyethyl)
ethylene diamine,
N,N'-bis-(2-hydroxyethyl) ethylene diamine, N-(3-hydroxybutyl) tetramethylene
diamine, etc.
Specific examples of the heterocyclic-substituted polyamines (2) are N-2-
aminoethyl piperazine,
N-2 and N-3 amino propyl morpholine, N-3-(dimethylamino) propyl piperazine, 2-
heptyl-3-(2-
aminopropyl) imidazoline, 1,4-bis (2-aminoethyl) piperazine, 1-(2-hydroxy
ethyl) piperazine, and
2-heptadecyl-l-(2-hydroxyethyl)-imidazoline, etc. Specific examples of the
aromatic po:lyamines
(3) are the various isomeric phenylene diamines, the various isomeric
naphthalene diamines, etc.
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Many patents have described suitable polyamine detergents including US Patents
3 172 892; 3 219 666; 3 272 746; 3 310 492; 3 341 542; 3 444 170; 3 455 831; 3
455 832;
3 576 743; 3 630 904; 3 632 511; 3 804 763 and 4 234 435, and including
European patent
applications EP 0 336 664 and EP 0 263 703. A typical and preferred compound
of this class is
that made by reacting a poly(isobutylene)-substituted succinic anhydride
acylating agent (e.g.
anhydride, acid, ester, etc.) wherein the poly(isobutene) substituent has
between about 50 to
about 200 carbon atoms with a mixture of ethylene polyamines having 3 to about
10 amino
nitrogen atoms per ethylene polyamine and about 1 to about 6 ethylene groups.
The polyamine component may be defined by the average number of nitrogen atoms
per
molecule of the component , which may preferably be in the range of 4 to 8.5,
more preferably
6.8 to 8, especially 6.8 to 7.5 nitrogens per molecule.
Also suitable are materials made from amine mixtures comprising polyamines
having
seven and eight, and optionally nine, nitrogen atoms per molecule (so-called
'heavy' polyamines).
Preferably, the polyamine mixture comprises at least 45% and preferably 50% by
weight
of polyamines having seven nitrogen atoms per molecule, based on the total
weight of
polyamines. In addition to polyamine mixtures, single species may also be
used, for example
TEPA and TETA.
A preferred polyamine detergent comprises the reaction product between a
poly(isobutene) substituted succinic anhydride acylating agent with a
polyamine or mixture of
polyamines as hereinbefore described. Preferably, the poly(isobutene) has a
number average
molecular weight (Mn) of about 400-2500, preferably 400-1300, such as about
950.
(c) The acidic organic species.
A range of acidic organic species have been found to be effective in the
present invention.
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One class of species are unsaturated, monocarboxylic acids, particularly
aliphatic acids
having between 8 and 30 carbon atoms. Preferred in this class are the fatty
acids, preferably fatty
acids with 12 to 22 carbon atoms. Examples include lauric acid, palmitoleic
acid, oleic acid,
elaidic acid, petroselic acid, ricinoleic acid, elaeostearic acid, linoleic
acid, linolenic acid,
gadoleic acid, or erucic acid. Mixtures of fatty acids such as those obtained
from natural sources
are also suitable. Examples include rape-seed oil fatty acid, soya fatty acid
and tall oil fatty acid.
Saturated carboxylic acids are also suitable with the proviso that saturated
acids
containing straight-chains of 10 or more carbon atoms have been found not to
be effective. Non-
limiting examples include acetic acid, propionic acid, butyric acid,
Acids, if unsaturated, may be linear or branched. Saturated acids, provided
that the
proviso above is applied may be linear, or they may be branched. Non-limiting
examples of
branched acids include neodecanoic acid and neo-tridecoanoic acid.
Polycarboxylic acids are also suitable, for example hydrocarbyl-substituted
succinic acids
or dimer, trimer and higher oligomer acids derived from fatty acids.
Acids comprising aromatic ring systems are also suitable. Non-limiting
examples include
benzoic acid, salicylic acid and similar.
Non-aromatic, cyclic acids may be used. These may be single rings or fused
ring
structures and may contain unsaturation. Non-limiting examples include
naphthenic acids and
resin acids such as abietic acid, dihydroabietic acid, tetrahydroabietic acid,
dehydroabietic acid,
neoabietic acid, pimaric acid, levopimaric acid, parastrinic acid and similar.
In a preferred embodiment, the acidic organic species comprises an
unsaturated,
monocarboxylic acid having between 8 and 30 carbon atoms, preferably between
12 and 22
carbon atoms.
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The fuel oil
The fuel oil may be, e.g., a petroleum-based fuel oil, especially a middle
distillate fuel oil.
Such distillate fuel oils generally boil within the range of from 110 C to 500
C, e.g. 150 C to
400 C.
The invention is applicable to middle distillate fuel oils of all types,
including the broad-
boiling distillates, i.e., those having a 90%-20% boiling temperature
difference, as measured in
accordance with ASTM D-86, of 50 C or more.
The fuel oil may comprise atmospheric distillate or vacuum distillate, cracked
gas oil, or a
blend in any proportion of straight run and thermally and/or catalytically
cracked distillates. The
most common petroleum distillate fuels are kerosene, jet fuels, diesel fuels,
heating oils and
heavy fuel oils. The heating oil may be a straight atmospheric distillate, or
may also contain
vacuum gas oil or cracked gas oil or both. The fuels may also contain major or
minor aniounts of
components derived from the Fischer-Tropsch process. Fischer-Tropsch fuels,
also known as FT
fuels, include those that are described as gas-to-liquid fuels, coal and/or
biomass conversion fuels.
To make such fuels, syngas (CO + H2) is first generated and then converted to
normal paraffins
and olefins by a Fischer-Tropsch process. The normal paraffins may then be
modified by
processes such as catalytic cracking/reforming or isomerisation, hydrocracking
and
hydroisomerisation to yield a variety of hydrocarbons such as iso-paraffins,
cyclo-paraffins and
aromatic compounds. The resulting FT fuel can be used as such or in
combination with other
fuel components and fuel types such as those mentioned in this specification.
T'he above
mentioned low temperature flow problem is most usually encountered with diesel
fuels and with
heating oils. The invention is also applicable to fuel oils containing fatty
acid methyl esters
derived from vegetable oils, for example, rapeseed methyl ester, either used
alone or in admixture
with a petroleum distillate oil.
The fuel oil is preferably a low sulphur content fuel oil. Typically, the
sulphur content of
the fuel oil will be less than 500ppm (parts per million by weight).
Preferably, the sulphur content
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of the fuel will be less than 100ppm, for example, less than 50ppm. Fuel oils
with even lower
sulphur contents, for example less that 20ppm or less than 10ppm are also
suitable.
Treat Rates
The amounts of each component present in the fuel oil will depend on the
nature of the
species used, the properties of the fuel oil and the low temperature
performance required. As
discussed hereinabove, the present invention is based on the observation of a
negative impact on
the low temperature behaviour of the wax anti-settling additive when present
in premium diesel
fuels which contain relatively high levels of polyamine detergent.
Typically, the amount of (b) at least one polyamine detergent in the fuel oil
coniposition
will be in excess of 50ppm by weight based on the weight of the fuel oil, for
example in excess of
75ppm by weight or 100ppm by weight. Some premium diesel fuels may contain up
to 500 ppm
by weight of polyamine detergent. This can be compared to a treat rate of
around 10 -75 ppm for
more conventional, non-premium diesel fuels.
The amount of (a) at least one polar nitrogen compound effective as a wax anti-
settling
additive will typically be in the range of 10 - 300 ppm, preferably 10 - 100
ppm by weight based
on the weight of the fuel oil.
The amount of (c) used will typically be in the range of 5 - 200, preferably,
5 - 150, more
preferably 5 - 100, for example 10 - 50 ppm by weight based on the weight of
the fuel oil.
Other additives
It is commonplace in the art to use polar nitrogen compounds effective as a
wax anti-
settling additives in combination with other additional cold-flow improving
additives. Suitable
materials will be well known to those skilled in the art and include for
example, ethylene-
unsaturated ester copolymers such as EVA and similar polymers. The present
invention
contemplates the addition of such additional cold-flow improving additives;
their application in
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PF2006M014 FF 15
terms of treat rate being also well known to those skilled in the art. In an
embodiment of all
aspects of the invention, the fuel oil further comprises an ethylene-
unsaturated ester copolymer.
Evaluation of low temperature properties.
The method of the first aspect, the uses of the second and third aspects and
the process of
the fourth aspect all require that the low temperature properties of the fuel
oil composition be
measured. As is known in the art, there are a number of methods which can be
used to determine
the low temperature properties of a fuel oil. Preferably, the low temperature
properties are as
determined by measuring OCP, CFPP, or both. Preferably, the low temperature
properties
improved in all aspects of the present invention are ACP, CFPP, or both.
ACP is a measurement of the propensity of the wax content of a fuel oil to
settle and
thus a determination of the effectiveness of a wax anti-settling additive. To
determine ACP, the
cloud point (CP) of a base fuel oil is measured. The wax anti-settling
additive under study is then
added to the base fuel and the sample cooled to a temperature below the
measured CP. This
temperature may vary, in Germany a temperature of -13 C is commonly used, in
South Korea it
may be -15 or -20 C and a value of -18 C is also often used. After leaving the
fuel oil sample for
a time to allow any wax to settle, the CP of the bottom 20% by volume of the
sample is measured.
The difference between this measurement and the value obtained for the base
fuel is ACP. A
small value, preferably around zero, of ACP indicates good wax dispersancy.
CFPP is a standard industry test to evaluate the ability of a fuel oil sample
to flow through
a filter at reduced temperature. The test which is carried out by the
procedure described in detail
in "Jn. Of the Institute of Petroleum ", vol. 52, No. 510 (1996), pp 173-285,
is designed to
correlate with the cold flow of a middle distillate in automotive diesels. In
brief, a sample of the
oil to be tested (40 cm3) is cooled in a bath which is maintained at about -34
C to give linear
cooling at about 1 C/min. Periodically (at each one degree centigrade starting
from above the
cloud point), the oil is tested for its ability to flow through a fine screen
in a prescribed time
period using a test device which is a pipette to whose lower end is attached
an inverted funnel
which is positioned below the surface of the oil to be tested. Stretched
across the mouth of the
CA 02614026 2007-12-12
PF2006M014 FF 16
funnel is a 350 mesh screen having an area defined by a 12 mm diameter. The
periodic tests are
initiated by applying a vacuum to the upper end of the pipette whereby oil is
drawn through the
screen up into the pipette to a mark indicating 20 cm3 of oil. After each
successful passage, the
oil is returned immediately to the CFPP tube. The test is repeated with each
one degree drop in
temperature until the oil fails to fill the pipette within 60 seconds, the
temperature at which
failure occurs being reported as the CFPP temperature.
The invention will now be described by way of example only.
In the experiments detailed below, a low-sulphur content diesel fuel
containing a fixed
amount (48 ppm) of a polar nitrogen compound effective as a wax anti-settling
additive and
varying amounts of a polyamine detergent was tested for ACP and CFPP. The
effect of adding
various amounts of an acidic organic species was determined.
The polar nitrogen compound effective as a wax anti-settling used was an N,N-
dialkylammonium salt of 2-N',N' dialkylamidobenzoate, the product of reacting
one mole of
phthalic anhydride and two moles of di(hydrogenated tallow) amine.
The polyamine detergent used was a PIBSA-PAM detergent, the product of
reacting a
polyisobutylene-substituted succinic anhydride, the polyisobutylene group
having a molecular
weight of ca. 1000, with a polyamine mixture predominating in species having
at least seven
nitrogen atoms per molecule.
For all tests, the diesel fuel also contained fixed amounts of additional cold-
flow additives.
These are typical of additives routinely used in commercial diesel fuels and
were mainly
ethylene-unsaturated ester co-polymers and fumarate vinyl acetate co-polymers.
All amounts are
given in ppm of active ingredient (i.e. ingredient which is not solvent or
carrier) by weight, based
on the weight of the fuel.
For the wax anti-settling tests, the fuel was cooled to -18 C.
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PF2006MOI4 FF 17
Table 1 below gives results showing the effect of an acidic organic species
comprising a
mixture of fatty acids predominating in straight-chain C18 mono- and di-
unsaturated mono-
carboxylic acids.
Example detergent/ppm acid/ppm CFPP / C ACP / C
1 0 0 -26.5 0.6
2 84 0 -23.7 3. 3
3 108 0 -23.5 64
4 127 0 -20.0 8.1
0 10 -24.5 0.4
6 84 10 -24.5 0.6
7 108 10 -25.8 1.2
8 127 10 -23.0 1.4
9 0 25 -27.0 0.3
84 25 -25.0 0.9
11 127 25 -22.5 0.9
12 0 50 -25.0 1.1
13 84 50 -23.0 0.5
14 127 50 -23.0 1.0
0 100 -23.5 0.3
16 84 100 -25.5 0.8
17 127 100 -22.0 1.4
18 108 125 -29.0 1.6
19 0 150 -26.5 0.6
84 150 -23.0 1.0
21 127 150 -22.0 1.7
5 Table 1
From Table 1, it can be seen that in the absence of the organic acidic
species, increasing
amounts of detergent lead to a general decrease in CFPP and a marked increase
in OCP
CA 02614026 2007-12-12
PF2006M014 FF 18
(Comparative Examples 1-4). This demonstrates the loss in low-temperature
properties associated
with the combined use of the WASA with the polyamine detergent. The addition
of the acid in
the absence of the detergent had some effect on CFPP but no noticeable effect
on ACP (compare
Examples 1, 5, 9, 12, 15 & 19). The data in the table clearly show that the
addition of the acid to
the fuel in the presence of the detergent and the WASA mitigates the loss in
low-temperature
properties. For example, compare Example 2 with Examples 6, 10, 13, 16 & 20
which all contain
84 wppm of detergent, or Example 4 with Examples 8, 11, 14, 17 & 21 which all
contain 127
wppm of detergent.
In Table 2 below, the acid used was a neodecanoic acid. All other species were
the same
as used in Table 1.
Example detergent/ppm acid/ppm CFPP / C ACP / C
1 0 0 -26.5 0,. 6
2 84 0 -23.7 3.3
3 108 0 -23.5 6.4
4 127 0 -20.0 8.1
22 0 25 -26.0 0.2
23 84 25 -21.5 0.7
24 127 25 -25.0 4.6
25 0 100 -27.0 0.2
26 84 100 -24.0 1.0
27 127 100 -23.0 3.9
Table 2
The results of Table 2 show a similar trend to those of Table 1.
Table 3 shows the results for several other organic acids. As with Tables 1
and 2, all show
an improvement in either CFPP, OCP or both compared to Comparative Examples 1-
4.
CA 02614026 2007-12-12
PF2006M014 FF 19
Example detergent/ppm Acid(*) /ppm CFPP / C ACP / C
1 0 0 -26.5 0.6
2 84 0 -23.7 3.3
3 108 0 -23.5 6.4
4 127 0 -20.0 8.1
28 0 (A) 150 -28.0 0.3
29 84 (A) 150 -23.0 0.5
30 127 (A) 150 -24.0 0.6
31 108 (D) 10 -25.0 1.5
32 108 (D) 60 -28.5 2.9
33 108 (D) 125 -29.5 1.5
34 108 (E) 60 -28.5 3.0
35 108 (E) 125 -27.0 2.9
36 108 (F) 15 -23.0 2.8
37 108 (F) 30 -22.5 2.3
38 108 (F) 60 -26.5 2.9
39 108 (F) 125 -28.5 2.8
40 108 (G) 60 -25.5 1.3
41 108 (G) 125 -24.0 1.0
42 108 (H) 10 -24.5 4.6
43 0 (1)25 -24.5 0.2
44 84 (I) 25 -22.5 0.7
45 127 (1)25 -21.5 2.0
46 0 (J) 75 -29.0 0.6
47 84 (J) 75 -24.0 1.0
48 127 (J) 75 -20.0 2.8
Table 3
[* (A) = propionic acid, (D) = oleic acid, (E) =linoleic acid, (F) = Tall oil
fatty acid, (G) = soya: fatty acid,
(H) = salicylic acid, (I) = dodecyl succinic acid (J) = polyisobutylene
succinic diacid]
