Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Fuel Oil Compositions
This invention relates to fuel oil, especially middle distillate fuel oil,
compositions of
improved performance.
More demanding requirements are being placed on fuel oil combustion devices,
such as
diesel engines, for improved performance, particularly in the areas of
particulate matter
emission and smoke reduction, reduced engine wear and improved fuel economy.
Combustors, such as heating units, fueled by liquid fuels are also prone to
emission of
unburned or partially unburned substances especially when operated on a
frequent start-
stop programme or when the burner parts are inadequately maintained. As energy
regulations become more stringent the emissions by such units need also to be
minimised.
The use of additives, including metallic additives, in fuel oils to improve
its performance is
well known. Certain organometallic compounds are known to be effective
combustion
improvers for distillate fuels such as home heating oils. For example, US-A-
3,112,789
describes the use of cyclopentadienyl manganese tricarbonyls for this purpose.
While GB-
A-1,090,289 and US-A-3,637,356 describe the use of calcium compounds for
reducinQ
smoke.
EP-B-O 476 196 describes an additive composition for hydrocarbonaceous fuel
comprising
(a) one or more fuel-soluble manganese carbonyl compounds;
(b) one or more fuel-soluble alkali or alkaline earth metal containing
detergents;
and
(c) one or more fuel-soluble ashless dispersants;
and its use for reducing the soot, smoke and/or carbonaceous products produced
on
combustion of the fuel and for reducing the acidity of the carbonaceous
products.
Canadian Patent No. 1,188,891 describes an additive comprising at least one
oil-soluble
and/or dispersible compound of a transition metal and/or alkaline earth metal
as well as one
of several inhibitors against polymerisation and oxidation of hydrocarbons
which inhibits
CONFIRMATION COPY
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the formation of soot. Examples 1 and 2 disclose compositions containing
overbased
(carbonated) barium sulfonate.
GB-A-2 248 068 discloses an additive for reducing smoke and particulate
emissions during
combustion of a fuel oil which comprises:
(a) a compound of an alkali metal;
(b) a compound of a metal of group 2a of the Periodic Table; and
(c) a compound of a transition metal selected from groups 1 b, 3b. 4b, 5b, 6b,
7b
and 8 of the Periodic Table.
GB-A-2 321 906 discloses a fuel additive comprising (a) a calcium salt and (b)
an alkali
and/or alkaline earth metal salt other than one of calcium.
WO 96/34074, WO 96/34075 and WO 97/40122 disclose fuel additives for reducing
the
emission of particulates.
GB-A-2 091 291 discloses an additive for a diesel fuel oil, which comprises a
fuel oil
soluble or dispersible calcium compound and a fuel oil soluble or dispersible
iron
compound, for smoke suppression.
These references, however, do not disclose the defined composition of the
present
invention.
Further, environmental concerns have led to a need for fuels with reduced
sulfur content,
especially diesel fuel and kerosene, which have resulted in an increase in the
number of
reported problems in fuel pumps in diesel engines. The problems are caused by
wear in,
for example, cam plates, rollers, spindles and drive shafts, and include
sudden pump
failures relatively early in the life of the engine. Historically, the sulfur
content in a diesel
fuel was a maximum of 0.2% by weight in Europe, but recently sulfur levels
have been
reduced to at most 0.05% by weight, and further reductions are expected.
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The performance specifications for fuel oils, such as diesel fuel oils, are
also being
regularly revised with tighter targets and fewer debits. For example, fuel oil
compositions
demonstrating control of haze and/or foaming tendency are sought.
There is, therefore, a constant need for fuel oil compositions with improved
performance to
meet the developments in environmental and performance regulations; this is
especially the
case for the middle distillate fuel oils, such as diesel fuel oils and heating
oils.
Further, there is an on-going demand to minimise the cost of additives used,
and reduce the
amount of metals used in fuel oils, for example, in order to reduce the
formation of ash
deposits upon combustion.
The present invention meets this need by providing a fuel oil composition
comprising
middle distillate fuel oil and incorporated therein an additive composition
comprising at
least two or more compounds selected from the group consisting of (i) at least
one fuel-
soluble or fuel-dispersible neutral alkaline earth metal compound, (ii) at
least one fuel-
soluble or fuel-dispersible neutral alkali metal compound, and (iii) at least
one fuel-soluble
or fuel-dispersible transition metal compound. It has been surprisingly found
that such a
fuel oil composition provides better performance than fuel oil compositions
comprising
any one of the compounds (i) to (iii).
Accordingly, a first aspect of the present invention is a fuel oil composition
comprising
middle distillate fuel oil and incorporated therein an additive composition
comprising (a) at
least one fuel-soluble or fuel-dispersible neutral alkaline earth metal
compound and/or at
least one fuel-soluble or fuel-dispersible neutral alkali metal compound, and
(b) at least one
fuel-soluble or fuel-dispersible transition metal compound, characterised in
that the fuel oil
composition contains at most 0.05 mass % of sulfur, the total metal content
derived from
(a) and (b) in the fuel oil composition is at most 50 ppm by mass, and the
mass proportion
of (a) to (b), based on metal content, is in the range of from 1:99 to 99:1.
A second aspect of the present invention is a heating oil composition
comprising heating
oil and incorporated therein an additive composition comprising (a) at least
one fuel-
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soluble or fuel-dispersible neutral alkaline earth metal compound and/or at
least one fuel-
soluble or fuel-dispersible neutral alkali metal compound, and (b) at least
one fuel-soluble
or fuel-dispersible transition metal compound, characterised in that the fuel
oil composition
contains at most 0.2 mass % of sulfur, the total metal content derived from
(a) and (b) in
the heating oil composition is at most 50 ppm by mass, and the mass proportion
of (a) to
(b), based on metal content, is in the range of from 1:99 to 99:1.
A third aspect of the present invention a process for reducing particulate
matter emissions
and/or smoke during operation of a fuel oil combustion device which comprises
adding to
the device a fuel oil composition as defined in the first or second aspect.
A fourth aspect of the present invention is the use of a fuel oil composition
as defined in
the first or second aspect to reduce particulate matter emissions during
operation of a fuel
oil combustion device.
Fuel Oils
In principle, the advantages of this invention may be achieved in any
distilled or distillable
liquid hydrocarbonaceous fuel derived from petroleum, coal, shale and/or tar
sands and
bio-fuel. In most instances, at least under present circumstances, the base
fuels will be
derived primarily, if not exclusively, from petroleum.
The invention is thus applicable to such fuels as gasoline, kerosine, jet
fuel, aviation fuel,
diesel fuel, home heating oil, light cycle oil, heavy cycle oil, light gas
oil, heavy gas oil,
and in general, any liquid hydrocarbonaceous product suitable for combustion
in either an
engine or in a burner apparatus.
Middle distillate fuel oils, as a class of fuels, generally boil within the
range of about
100 C to about 500 C, e.g. 150 to about 400 C, for example, those having a
relatively
high Final Boiling Point of above 360 C (ASTM D-86). Middle distillates
contain a
spread of hydrocarbons boiling over a temperature range, including n-alkanes
which
precipitate as wax as the fuel cools. They may be characterised by the
temperatures at
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which various %'s of fuel have vaporised, e.g. 10% to 90%, being the interim
temperatures
at which a certain volume % of initial fuel has distilled. The difference
between say 90%
and 20% distillation temperature may be significant. They are also
characterised by pour,
cloud and CFPP points, as well as their initial boiling point (IBP) and final
boiling point
(FBP). The petroleum 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 middle distillate fuels are
jet fuels,
diesel fuels and heating oils.
The heating oil may be a straight atmospheric distillate, or it may contain
minor amounts,
e.g. up to 35 mass %, of vacuum gas oil or cracked gas oils or of both.
Heating oils may be
made of a blend of virgin distillate, e.g. gas oil, naphtha, etc. and cracked
distillates, e.g.
catalytic cycle shock.
A representative specification for a diesel fuel includes a minimum flash
point of 38 C and
a 90% distillation point between 282 and 380 C (see ASTM Designations D-396
and D-
975).
The fuel oil may also be an animal or vegetable oil, or a mineral oil as
described above in
combination with an animal or vegetable oil. Fuels from animal or vegetable
sources are
known as biofuels and are believed to be less damaging to the environment on
combustion,
and are obtained from a renewable source. It has been reported that on
combustion less
carbon dioxide is formed than is formed by the equivalent quantity of
petroleum distillate
fuel, e.g. diesel fuel, and very little sulfur dioxide is formed. Certain
derivatives of
vegetable oil, for example rapeseed oil, e.g. those obtained by saponification
and re-
esterification with a monohydric alcohol, may be used as a substitute for
diesel fuel. It has
recently been reported that mixtures of a rapeseed ester, for example,
rapeseed methyl ester
(RME). with petroleum distillate fuels in ratios of, for example, 10:90 by
volume are likely
to be commercially available in the near future.
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Thus, a biofuel is a vegetable or animal oil or both or a derivative thereof,
particularly an
oil comprising fatty acid and/or fatty acid esters. Vegetable oils are mainly
triglycerides of
monocarboxylic acids, e.g. acids containing 10-25 carbon atoms and listed
below
CH,OCOR
I
CHOCOR
I
CH2OCOR
where R is an aliphatic radical of 10-25 carbon atoms which may be saturated
or
unsaturated.
Generally, such oils contain glycerides of a number of acids, the number and
kind varying
with the source vegetable of the oil.
Examples of oils are rapeseed oil, coriander oil, soyabean oil, cottonseed
oil, sunflower oil,
castor oil, olive oil, peanut oil, maize oil, almond oil, palm kernel oil,
coconut oil, mustard
seed oil, beef tallow and fish oils. Rapeseed oil, which is a mixture of fatty
acids partially
esterified with glycerol, is preferred as it is available in large quantities
and can be obtained
in a simple way by pressing from rapeseed.
Examples of derivatives thereof are alkyl esters, such as methyl esters, of
fatty acids of the
vegetable or animal oils. Such esters can be made by transesterification.
As lower alkyl esters of fatty acids, consideration may be given to the
following, for
example as commercial mixtures: the ethyl, propyl, butyl and especially methyl
esters of
fatty acids with 12 to 22 carbon atoms, for example of lauric acid, myristic
acid, palmitic
acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, petroselic
acid, ricinoleic acid,
elaeostearic acid, linoleic acid, linolenic acid, eicosanoic acid, gadoleic
acid, docosanoic
acid or erucic acid, which have an iodine number from 50 to 150, especially 90
to 125.
Mixtures with particularly advantageous properties are those which contain
mainly, i.e. to
at least 50 mass % methyl esters of fatty acids with 16 to 22 carbon atoms and
1, 2 or 3
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double bonds. The preferred lower alkyl esters of fatty acids are the methyl
esters of oleic
acid, linoleic acid, linolenic acid and erucic acid.
Commercial mixtures of the stated kind are obtained for example by cleavage
and
esterification of natural fats and oils by their transesterification with
lower aliphatic
alcohols. For production of lower alkyl esters of fatty acids it is
advantageous to start from
fats and oils with high iodine number, such as, for example, sunflower oil,
rapeseed oil,
coriander oil, castor oil, soyabean oil, cottonseed oil, peanut oil or beef
tallow. Lower
alkyl esters of fatty acids based on a new variety of rapeseed oil, the fatty
acid component
of which is derived to more than 80 mass % from unsaturated fatty acids with
18 carbon
atoms, are preferred.
Preferably the biofuel is present in an amount of up to 50 mass % based on the
mass of the
middle distillate fuel oil, more preferably of up to 10 mass %, especially up
to 5 mass %.
The fuel oil composition, for example, diesel fuel oil, generally has a sulfur
level of 0.2
mass % or less (as measured by X-ray Fluorescence according to ASTM D2622-94)
based
on the mass of the fuel oil composition. Preferably, the fuel oil composition
contains at
most 0.1 mass % of sulfur; more preferably at most 0.05 mass %; advantageously
at most
0.04 mass %; more advantageously at most 0.03 mass %; especially at most 0.02
mass %;
such as less than 0.01 mass % of sulfur. Fuels oil compositions containing
even lower
sulfur levels, for example 75 ppm by mass or less, 50 ppm or less and 25 ppm
or less, are
also within the scope of the present invention.
Typically the heating oil compositions of the present invention contain a
sulfur level of at
most 0.2 mass % (as measured by X-ray Fluorescence according to ASTM D2622-94)
based on the mass of the heating oil composition. Preferably, the heating oil
composition
contains at most 0.1 mass % of sulfur; more preferably at most 0.05 mass %;
advantageously at most 0.04 mass %.
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The art describes methods for reducing the sulfur concentration of hydrocarbon
middle
distillate fuels, such methods including solvent extraction, sulfuric acid
treatment, and
hydrodesulfurisation.
Fuel oils having such low sulfur levels show good response to the additive
compositions of
the present invention despite the reduced tendency of such fuel oils to
produce particulate
emissions.
Hydrocarbon middle distillate fuel oils, as used herein refers to middle
distillate fuel oils
which are substantially free, and preferably free, of ethers and/or alcohols.
As used herein
the term 'substantially free' with reference to ethers and/or alcohols in fuel
oil refers to an
amount of up to 20 mass % based on the mass of the middle distillate fuel oil,
preferably
up to 10 mass %, more preferably up to 5 mass %.
Preferably, the fuel oil is middle distillate fuel, such as a hydrocarbon
middle distillate fuel
oil; more preferably, the fuel oil is diesel fuel oil or heating oil.
Combustion Devices
In all aspects of the present invention, the fuel oil compositions can be used
in combustion
devices operated by compression ignition mechanisms, as well as those operated
by non-
compression mechanisms.
An example of a combustion device operated by compression ignition mechanism
is the
internal combustion engine which is used to power mobile vehicles. While an
example of
a non-compression combustion device is a stationary burner.
Neutral Alkaline Earth Metal and Neutral Alkali Metal Compounds
The type of neutral alkaline earth metal and neutral alkali metal compounds of
the present
invention is not important provided that the combination of the compounds
making up the
additive compositions of the present invention (including the transition metal
compound)
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are soluble or dispersible in the fuel oil in which it is to be used at the
concentration in
which it is to be used.
In all aspects of the invention, the alkaline earth metal particularly
suitable in the present
invention is selected from the group consisting of calcium and magnesium.
Preferably the
alkaline earth metal compound is a calcium compound.
In all aspects of the invention, the alkali metal particularly suitable in the
present invention
is selected from the group consisting of lithium, sodium and potassium.
Preferably the
alkali metal compound is a sodium or potassium compound, more preferably a
sodium
compound.
Preferably the neutral alkaline earth metal and neutral alkali metal compounds
are salts of
organic acids. As examples of organic acids, there may be mentioned carboxylic
acids and
anhydrides thereof, phenols, sulfurised phenols, salicylic acids and
anhydrides thereof,
alcohols, dihydrocarbyldithiocarbamic acids, dihydrocarbyldithiophosphoric
acids,
dihydrocarbylphosphonic acids, dihydrocarbylthiophosphonic acids and sulfonic
acids.
The term 'neutral' as used herein refers to metal compounds, preferably metal
salts of
organic acids, that are stoichiometric or predominantly neutral in character,
that is most of
the metal is associated with an organic anion. For a metal compound to be
completely
neutral, the total number of moles of the metal cation to the total number of
moles of
organic anion associated with the metal will be stoichiometric. For example,
for every one
mole of calcium cations there should be two moles of sulfonate anions.
The metal salts of the present invention include predominantly neutral salts
where minor
amounts of non-organic anions, for example carbonate and/or hydroxide anions,
may also
be present provided their presence does not alter the predominantly neutral
character of the
metal salt.
Thus, metal salts of the present invention preferably have a metal ratio of
less than 2, more
preferably less than 1.95, especially less than 1.9, advantageously less than
1.8, more
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especially less than 1.6, for example less than 1.5, such as less than 1.4 or
less than 1.35.
The metal ratio is preferably at least about 1Ø The metal ratio, as used
herein, is the ratio
of total metal to the metal associated with the organic anion. So metal salts
having a metal
ratio of less than 2 have greater than 50% of the metal associated with the
organic anion.
The metal ratio can be calculated by
a) measuring the total amount of metal in the neutral metal salt; and then
b) determining the amount of metal associated with the organic.
Suitable methods for measuring the total metal content are well known in the
art and
include X-ray fluorescence and atomic absorption spectrometry.
Suitable methods for determining the amount of metal associated with the
organic acid
include potentiometric acid titration of the metal salt to determine the
relative proportions
of the different basic constituents (for example, metal carbonate and metal
salt of organic
acid); hydrolysis of a known amount of metal salt and then the potentiometric
base titration
of the organic acid to determine the equivalent moles of organic acid; and
determination of
the non-organic anions, such as carbonate, by measuring the CO2 content.
In the case of a metal sulfonate, ASTM D3712 may be used to determine the
metal
associated with the sulfonate.
In the instance where a composition comprises one or more neutral metal salts
and one or
more co-additives, then the neutral metal salt(s) may be separated from the co-
additives,
for example, by using dialysis techniques and then the neutral metal salt may
be analysed
as described above to determine the metal ratio. Background information on
suitable
dialysis techniques is given by Amos, R. and Albaugh, E. W. in "Chromatography
in
Petroleum Analysis" Altgelt, K. H. and Gouw, T. H., Eds., pages 417 to 421,
Marcel
Dekker Inc., New York and Basel, 1979.
Specific examples of organic acids include surfactant molecules, examples of
which are
hydrocarbyl sulfonic acids, hydrocarbyl substituted phenols, hydrocarbyl
substituted
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sulfurised phenols, hydrocarbyl substituted salicylic acids,
dihydrocarbyldithiocarbamic
acid. dihydrocarbyldithiophosphoric acid, and aliphatic and aromatic
carboxylic acids.
The neutral metal salts of the present invention may be salts of one type of
surfactant or
salts of more than one type of surfactant. Preferably, they are salts of one
type of
surfactant.
Sulfonic acids used in accordance with this aspect of the invention are
typically obtained
by sulfonation of hydrocarbyl-substituted, especially alkyl-substituted,
aromatic
hydrocarbons, for example, those obtained from the fractionation of petroleum
by
distillation and/or extraction, or by the alkylation of aromatic hydrocarbons.
Examples
include those obtained by alkylating benzene, toluene, xylene, naphthalene,
biphenyl or
their halogen derivatives, for example, chlorobenzene, chlorotoluene or
chloronaphthalene.
Alkylation of aromatic hydrocarbons may be carried out in the presence of a
catalyst with
alkylating agents having from about 3 to more than 100 carbon atoms, such as,
for
example, haloparaffins, olefins that may be obtained by dehydrogenation of
paraffins, and
polyolefins, for example, polymers of ethylene, propylene, and/or butene. The
alkylaryl
sulfonic acids usually contain from about 22 to about 100 or more carbon
atoms; preferably
the alkylaryl sulfonic acids contain at least 26 carbon atoms, especially at
least 28, such as
at least 30, carbon atoms. The sulfonic acids may be substituted by more than
one alkyl
group on the aromatic moiety, for example they may be dialkylaryl sulfonic
acids. The
alkyl group preferably contains from about 16 to about 80 carbon atoms, with
an average
number of carbon atoms in the range of from 36-40, or an average carbon number
of 24,
depending on the source from which the alkyl group is obtained. Preferably the
sulfonic
acid has a number average molecular weight of 350 or greater, more preferably
400 or
greater, especially 500 or greater, such as 600 or greater. Number average
molecular
weight may be determined by ASTM D3712.
When neutralising these alkylaryl sulfonic acids to provide sulfonates,
hydrocarbon
solvents and/or diluent oils may also be included in the reaction mixture, as
well as
promoters.
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Another type of sulfonic acid which may be used in accordance with the
invention
comprises alkyl phenol sulfonic acids. Such sulfonic acids can be sulphurized.
Preferred
substituents in alkyl phenol sulfonic acids are substituents represented by R
in the
discussion of phenols below.
Sulfonic acids suitable for use in accordance with the invention also include
alkyl sulfonic
acids. In such compounds the sulfonic acid suitably contains 22 to 100 carbon
atoms,
advantageously 25 to 80 carbon atoms, especially 30 to 60 carbon atoms.
Preferably the sulfonic acid is hydrocarbyl-substituted aromatic sulfonic
acid, more
preferably alkyl aryl sulfonic acid.
Phenols used in accordance with the invention may be non-sulphurized or,
preferably,
sulphurized. Further, the term "phenol" as used herein includes phenols
containing more
than one hydroxyl group (for example, alkyl catechols) or fused aromatic rings
(for
example, alkyl naphthols) and phenols which have been modified by chemical
reaction, for
example, alkylene-bridged phenols and Mannich base-condensed phenols; and
saligenin-
type phenols (produced by the reaction of a phenol and an aldehyde under basic
conditions).
Preferred phenols from which neutral calcium and/or magnesium salts in
accordance with
the invention may be derived are of the formula
OH
(R)y
where R represents a hydrocarbyl group and y represents 1 to 4. Where y is
greater than 1,
the hydrocarbyl groups may be the same or different.
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The phenols are frequently used in sulphurized form. Sulphurized hydrocarbyl
phenols
may typically be represented by the formula:
OH OH
(S)X
(R)y (R)y
where x, represents an integer from 1 to 4. In some cases, more than two
phenol molecules
may be linked by (S), bridges, where S represents a sulfur atom.
In the above formulae, hydrocarbyl groups represented by R are advantageously
alkyl
groups, which advantageously contain 5 to 100 carbon atoms, preferably 5 to 40
carbon
atoms, especially 9 to 12 carbon atoms, the average number of carbon atoms in
all of the R
groups being at least about 9 in order to ensure adequate solubility or
dispersibility in oil.
Preferred alkyl groups are nonyl (e.g. tripropylene) groups or dodecyl (e.g.
tetrapropylene)
groups.
In the following discussion, hydrocarbyl-substituted phenols will for
convenience be
referred to as alkyl phenols.
A sulfurizing agent for use in preparing a sulphurized phenol or phenate may
be any
compound or element which introduces -(S)x- bridging groups between the alkyl
phenol
monomer groups, wherein x is generally from I to about 4. Thus, the reaction
may be
conducted with elemental sulfur or a halide thereof, for example, sulfur
dichloride or, more
preferably, sulfur monochloride. If elemental sulfur is used, the
sulfurisation reaction may
be effected by heating the alkyl phenol compound at from 50 to 250 C, and
preferably at
least 100 C. The use of elemental sulfur will typically yield a mixture of
bridging groups -
(S)X as described above. If a sulfur halide is used, the sulfurisation
reaction may be
effected by treating the alkyl phenol at from -10 C to 120 C, preferably at
least 60 C. The
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reaction may be conducted in the presence of a suitable diluent. The diluent
advantageously comprises a substantially inert organic diluent, for example
mineral oil or
an alkane. In any event, the reaction is conducted for a period of time
sufficient to effect
substantial reaction. It is generally preferred to employ from 0.1 to 5 moles
of the alkyl
phenol material per equivalent of sulfurizing agent.
Where elemental sulfur is used as the sulfurizing agent, it may be desirable
to use a basic
catalyst, for example, sodium hydroxide or an organic amine, preferably a
heterocyclic
amine (e.g., morpholine).
Details of sulfurisation processes are well known to those skilled in the art,
for example
US-A-4,228,022 and US-A-4,309,293.
As indicated above, the term "phenol" as used herein includes phenols which
have been
modified by chemical reaction with, for example, an aldehyde, and Mannich base-
condensed phenols.
Aldehydes with which phenols used in accordance with the invention may be
modified
include, for example, formaldehyde, propionaldehyde and butyraldehyde. The
preferred
aldehyde is formaldehyde. Aldehyde-modified phenols suitable for use in
accordance with
the present invention are described in, for example, US-A-5 259 967.
Mannich base-condensed phenols are prepared by the reaction of a phenol, an
aldehyde and
an amine. Examples of suitable Mannich base-condensed phenols are described in
GB-A-2
121 432.
In general, the phenols may include substituents other than those mentioned
above.
Examples of such substituents are methoxy groups and halogen atoms.
Salicylic acids used in accordance with the invention may be non-sulphurized
or
sulphurized, and may be chemically modified and/or contain additional
substituents, for
example, as discussed above for phenols. Processes similar to those for
phenols may also
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be used for sulfurizing a hydrocarbyl-substituted salicylic acid, and are well
known to
those skilled in the art. Salicylic acids are typically prepared by the
carboxylation, by the
Kolbe-Schmitt process, of phenoxides, and in that case, will generally be
obtained
(normally in a diluent) in admixture with uncarboxylated phenol.
Preferred substituents in oil-soluble salicylic acids from which neutral
calcium and/or
maQnesium salts in accordance with the invention may be derived are the
substituents
represented by R in the above discussion of phenols. In alkyl-substituted
salicylic acids,
the alkyl groups advantageously contain 5 to 100 carbon atoms, preferably 9 to
30 carbon
atoms, especially 14 to 20 carbon atoms.
Alcohols which may be used are mono- and polyols. The alcohols preferably have
sufficient number of carbon atoms to provide adequate oil solubility or
dispersibility to a
metal salt thereof. Preferred alcohols have at least 4 carbon atoms, an
example of which is
tertiary butyl alcohol.
Carboxylic acids which may be used in accordance with the invention include
mono- and
dicarboxylic acids. Preferred monocarboxylic acids are those containing 8 to
30 carbon
atoms, especially 8 to 24 carbon atoms. (Where this specification indicates
the number of
carbon atoms in a carboxylic acid, the carbon atom(s) in the carboxylic
group(s) is/are
included in that number.) Examples of monocarboxylic acids are iso-octanoic
acid, stearic
acid, oleic acid, palmitic acid and behenic acid. Iso-octanoic acid may, if
desired, be used
in the form of the mixture of C8 acid isomers sold by Exxon Chemical under the
trade
name "Cekanoic". Other suitable acids are those with tertiary substitution at
the a-carbon
atom and dicarboxylic acids with 2 or more carbon atoms separating the
carboxylic groups.
Further, dicarboxylic acids with more than 35 carbon atoms, for example, 36 to
100 carbon
atoms, are also suitable. Unsaturated carboxylic acids can be sulphurized.
Specific examples of carboxylic acids include alkyl and alkenyl succinic acids
and
anhydrides thereof. Also applicable are aromatic carboxylic acids such as
naphthenic acids
and hydrocarbyl derivatives thereof.
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The organic acids described in GB-A-2,248,068.
In the instance where more than one type of surfactant is present in the metal
salt, the
proportion of any one type of surfactant to another is not critical provided
the neutral
character of the metal is not altered.
It will be appreciated by one skilled in the art that a single type of
surfactant may contain a
mixture of surfactants of the same type. For example, a sulfonic acid
surfactant may
contain a mixture of sulfonic acids of varying molecular weights. Such a
surfactant
composition is considered as one type of surfactant.
As used in this specification the term "hydrocarbyl" refers to a group having
a carbon atom
directly attached to the rest of the molecule and having a hydrocarbon or
predominantly
hydrocarbon character. Examples include hydrocarbon groups, including
aliphatic (e.g.
alkyl or alkenyl), alicyclic (e.g. cycloalkyl or cycloalkenyl), aromatic, and
alicyclic-
substituted aromatic, and aromatic-substituted aliphatic and alicyclic groups.
Aliphatic
groups are advantageously saturated. These groups may contain non-hydrocarbon
substituents provided their presence does not alter the predominantly
hydrocarbon
character of the group. Examples include keto, halo, hydroxy, nitro, cyano,
alkoxy and
acyl. If the hydrocarbyl group is substituted, a single (mono) substituent is
preferred.
Examples of substituted hydrocarbyl groups include 2-hydroxyethyl, 3-
hydroxypropyl,
4-hydroxybutyl, 2-ketopropyl, ethoxyethyl, and propoxypropyl. The groups may
also or
alternatively contain atoms other than carbon in a chain or ring otherwise
composed of
carbon atoms. Suitable hetero atoms include, for example, nitrogen, sulfur,
and,
preferably, oxygen.
In all aspect of the invention, the Total Base Number (TBN), as measured
according to
ASTM D2896, of the neutral alkaline earth metal compounds and neutral alkali
metal
3o compounds is at most 100, preferably at most 80. more preferably at most
70,
advantageously at most 60, such as less than 50.
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In all aspects of the invention, a preferred neutral alkaline earth metal
compound is calcium
sulfonate or calcium salicylate; especially preferred is a calcium sulfonate.
In all aspects of the invention, a preferred neutral alkali metal compound is
selected from
the group consisting of sodium sulfonate, sodium salicylate, potassium
sulfonate and
potassium salicylate.
Transition Metal Compounds
The type of transition metal compounds of the present invention is not
important provided
that the combination of the compounds making up the additive composition of
the present
invention (as defined in the first or second aspect) is soluble or dispersible
in the fuel oil in
which it is to be used at the concentration in which it is to be used.
In all aspects of the invention, the transition metal is preferably selected
from the group
consisting of iron, manganese, copper, molybdenum, cerium, chromium, cobalt,
nickel,
zinc, vanadium and titanium; more preferably, the transition metal is iron.
The compound of the transition metal is preferably selected from an organic
acid salt of a
transition metal; ferrocene (Fe[C5H5]2) or a derivative thereof; and a
manganese carbonyl
compound or a derivative thereof.
The organic acids suitable for the transition metal are the same as those
described above for
the neutral alkaline earth metal and alkali metals. Specific examples of
preferred transition
metal compounds of organic acids are iron naphthenate, iron oleate, copper
naphthenate,
copper oleate, copper dithiocarbamate, copper dithiophosphate, zinc
dithiophosphate, zinc
dithiocarbamate, molybdenum dithiocarbamate, molybdenum dithiophosphate,
cobalt
naphthenate, cobalt oleate, nickel oleate, nickel naphthenate, manganese
naphthenate and
manganese oleate. Also suitable are alkenyl and alkyl succinate salts of iron,
copper,
cobalt nickel and manganese.
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Other examples of transition metal compounds are 7t-bonded ring compounds
where the
number of carbon atoms in the ring may be in the range of from 2 to 8, such as
[CSHS],
[CGH4], [C8H8]. Examples are dibenzenechromium and dicyclopentadienyl
manganese.
Transition metal compounds with one Tt-bonded ring and other ligands such as
halogens,
CO, RNC annd R,P (where R is a hydrocarbyl group and may be the same or
different
when there is more than one R group) are also within the scope of the
invention. The 7c-
bonded ring may be heterocyclic such as [C4H4N], [CaH4P] and [C4H4S].
Examples of iron compounds include iron (II) and iron (III) compounds, and
derivatives of
ferrocene such as bis(alkyl substituted cyclopentadienyl) iron compounds, for
example
bis(methyl cyclopentadienyl) iron. Also compounds such as cyclopentadienyl
iron
carbonyl compounds, for example, [CSH5]Fe(CO)3 and [CSHS]Fe(CO)2Cl;
[CsH5][C4H4N]Fe; and [CSHS][C4H4P]Fe are suitable in the present invention.
Examples of manganese compounds and derivatives thereof include those
described in EP-
A-0,476,196. Specific examples are cyclopentadienyl manganese carbonyl
compounds
such as cyclopentadienyl manganese tricarbonyl and methyl cyclopentadienyl
manganese
tricarbonyl.
In an aspect of the present invention, the fuel oil composition does not
comprise a
manganese compound.
In all aspects of the invention, the fuel-soluble or fuel-dispersible
transition metal
compound is preferably ferrocene.
In the instance where two or more metal compounds are present in the additive
composition from any one of the categories of metal compounds, that is (i)
neutral alkaline
earth metal compounds, (ii) neutral alkali metal compounds and (iii)
transition metal
compounds, the compounds may be of the same or of different metals within the
category.
Concentration and Proportion
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In all aspects of the invention, the total amount of metal by mass, derived
from the or each
neutral alkaline earth metal compound and/or the or each neutral alkali metal
compound, in
the fuel oil composition is at most 25 ppm; preferably the total amount of
metal is at most
20 ppm, more preferably at most 15 ppm; advantageously at most 10 ppm;
especially at
most 7 ppm, such as at most 5 ppm, for example in the range of from 0.1 to 3
ppm or 0.5
to 3 ppm.
In all aspects of the invention, the total amount of metal by mass, derived
from the or each
transition metal compound, in the fuel oil composition is at most 25 ppm;
preferably the
total amount of metal is at most 20 ppm, more preferably at most 15 ppm;
advantageously
at most 10 ppm; especially at most 7 ppm, such as at most 5 ppm, for example
in the range
of from 0.1 to 3 ppm or 0.5 to 3 ppm.
Accordingly, the total amount of metal by mass, derived from the neutral
alkaline earth
metal compound and/or neutral alkali metal compound and transition metal
compound, in
the fuel oil composition, in all aspects of the invention, is preferably in
the range of from
0.1 to 50 ppm; preferably from 0.1 to 40 ppm; more preferably from 0.1 to 30
ppm;
advantageously from 0.1 to 20 ppm; more advantageously from 0.5 to 10 ppm;
especially
from 0.5 to 9 ppm; such as from 0.5 to 8 ppm. Also advantageous are fuel oil
compositions wherein the total amount of metal by mass, derived from the
neutral alkaline
earth metal compound and/or neutral alkali metal compound and transition metal
compound, in the fuel oil composition is in the range of from 0.5 to 7 ppm,
preferably from
0.75 to 6 ppm, advantageously from 1 to 5 ppm, such as from 1 to 4 ppm.
The amount of alkaline earth metal in the fuel oil composition is measured by
atomic
absorption; the amount of alkali metal in the fuel oil composition is measured
by atomic
absorption; and the amount of transition metal in the fuel oil composition is
measured by
atomic absorption.
A surprising feature of the present invention is that lower amounts of metal
can be used in
the fuel oil to achieve improved performance of the fuel oil.
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In all aspects of the invention, the mass proportion, based on metal content,
of (a) neutral
alkaline earth metal compound and/or neutral alkali metal compound to (b)
transition metal
compound is preferably in the range of from 10:90 to 90:10; more preferably in
the range
of from 20:80 to 80:20; advantageously from 30:70 to 70:30; for example in the
range of
from 40:60 to 60:40; more advantageously in the range of from 50:50 to 95:5;
especially in
the range of from 60:40 to 95:5; more especially in the range of from 70:30 to
95:5; such as
in the range of from 80:20 to 95:5; for example in the range of from 80:20 to
90:10.
It has been found that a particular proportion of (a) to (b) provides improved
performance
and that a higher proportion of the metal derived from (a) is preferred.
Additive Composition
The additive composition or concentrate comprising the metal compounds of the
present
invention may be in admixture with a carrier liquid (e.g. as a solution or a
dispersion).
Such concentrates are convenient as a means for incorporating the metal
compounds into
bulk fuel oil such as distillate fuel oil, which incorporation may be done by
methods known
in the art. The concentrates may also contain other fuel additives as required
and
preferably contain from 1 to 75 mass %, more preferably 2 to 60 mass %, most
preferably 5
to 50 mass % of the additives, based on active ingredient, preferably in
solution in the
carrier liquid. Examples of carrier liquids are organic solvents including
hydrocarbon
solvents, for example petroleum fractions such as naphtha, kerosene,
lubricating oil, diesel
fuel oil and heater oil; aromatic hydrocarbons such as aromatic fractions,
e.g. those sold
under the 'SOLVES SO' tradename; and paraffinic hydrocarbons such as hexane
and
pentane and isoparaffins. The carrier liquid must, of course, be selected
having regard to
its compatibility with the additives and with the fuel oil.
The metal compounds of the present invention may be incorporated into the bulk
fuel oil
by other methods such as those known in the art. If co-additives are required,
they may be
incorporated into the bulk fuel oil at the same time as the metal compounds of
the present
invention or at a different time.
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Accordingly, the present invention also provides a process for preparing a
fuel oil
composition as defined in the first or second aspect wherein the additive
composition as
defined in the first or second aspect is incorporated, preferably by blending
or mixing, into
a fuel oil, or the metal compounds of the present invention are incorporated ,
preferably by
blending or mixing, into the fuel oil contemporaneously or sequentially.
Co-Additives
The metal compounds of the present invention may be used in combination with
one or
more co-additives such as known in the art, for example the following: cold
flow
improvers, wax anti-settling agents, detergents, dispersants, antioxidants,
corrosion
inhibitors, dehazers, demulsifiers, metal deactivators, antifoaming agents,
cetane
improvers, cosolvents, package compatibilisers, other lubricity additives and
antistatic
additives. A particularly preferred co-additive is a polyisobutenyl
succinimide.
It should be appreciated that interaction may take place between any two or
more of the
metal compounds of the present invention after they have been incorporated
into the fuel
oil or additive composition, for example, between two different neutral
alkaline earth metal
compounds or between a neutral alkaline earth metal compound and a neutral
alkali metal
or between a neutral alkaline earth metal compound and a transition metal
compound or
between a neutral alkaline earth metal compound, a neutral alkali metal
compound and a
transition metal compound. The interaction may take place in either the
process of mixing
or any subsequent condition to which the composition is exposed, including the
use of the
composition in its working environment. Interactions may also take place when
further
auxiliary additives are added to the compositions of the invention or with
components of
fuel oil. Such interaction may include interaction which alters the chemical
constitution of
the metal compounds. Thus for example the compositions of the invention
include
compositions in which interaction between any of the metal compounds has
occurred, as
well as compositions in which no interaction has occurred between the
components mixed
in the fuel oil.
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The terms "comprising" or "comprises" when used herein is taken to specify the
presence
of stated features, integers, steps or components, but does not preclude the
presence or
addition of one or more other features, integers, steps, components or groups
thereof.
The terms "fuel-soluble" or "fuel-dispersible", as used herein with respect to
the metal
compounds, does not mean that the metal compounds are soluble, dissolvable,
miscible or
capable of being suspended in the fuel oil in all proportions. They do mean,
however, that
the metal compounds of the present invention are, for instance, soluble or
stable dispersible
in the fuel oil to an extent sufficient to exert their intended effect in the
environment in
which the fuel oil composition is employed. Moreover, the additional
incorporation of
other additives such as those described above may affect the fuel solubility
or dispersibility
of the metal compounds of the invention.
It has been found that the specific combination of neutral alkaline earth
metal compound
and transition metal compound, in particular a neutral calcium compound and an
iron
compound, is effective in a diesel fuel oil or a heating oil. Preferably the
neutral calcium
compound is calcium sulfonate and preferably has a Total Base Number (TBN), as
measured according to ASTM D2896, of at most 50, more preferably at most 30,
such as at
most 20; and the iron compound is preferably ferrocene.
An advantage of the present invention is that the use of expensive transition
metal
compounds in fuel oils can be minimised whilst still achieving effective
performance, for
example in the areas of particulate matter and/or smoke and lubricity.
Particulate matter emissions may be reduced by improved combustion of the fuel
oil,
which the metal compounds of the present invention play a role in promoting,
and/or
through after-treatment technologies of the exhaust gas, such as with a
particulate trap.
However, a drawback of the particulate trap method is the need for periodic
regeneration of
the trap to burn-off the deposited soot to keep the back-pressure within
acceptable limits.
This procedure makes the system costly, hard to control, and reduces the
durability of the
trap. The main problem in regenerating the trap is linked to the low exhaust
gas
temperature of diesel engines. The oxidation of diesel soot requires
temperatures of about
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600 C which is difficult to attain. Use of organometallic additives to reduce
the ignition
temperature of the soot has been described in the SAE paper 922188 by B.
Krutzsch and G.
Wenninger. Interestingly, the metal compounds of the present invention may be
useful in
improving the regenerative ability of a particulate matter trap. Many types of
the
particulate traps are known to those skilled in the art including as non-
limiting examples
"cracked-wall" and "deep-bed" ceramic types and sintered metal types.
Thus, the present invention also provides a process for reducing particulate
matter
emissions by improving the regenerative ability of a particulate trap of a
fuel oil
combustion device which process comprises supplying directly to the trap an
additive
composition as defined in the first aspect, and/or adding to the fuel oil
combustion device a
fuel oil composition as defined in the first aspect.
Similarly, the use of an additive composition as defined in the first aspect,
or a fuel oil
composition as defined in the first aspect to reduce particulate matter
emissions by
improving the regenerative ability of a particulate trap of a fuel oil
combustion device, is
also disclosed herein.
Further, the present invention provides a method of operating an apparatus
powered by a
diesel engine which is equipped with an exhaust system particulate trap and
optionally
equipped with a fuel additive dispenser, which method comprises supplying to
the diesel
engine a fuel oil composition as defined in the first aspect or when a fuel
dispenser is
present, maintaining a fuel additive composition as defined in the first
aspect in said
dispenser and blending said additive composition with a diesel fuel during
operation of the
diesel engine.
In another aspect, the present invention provides a process for improving the
combustion of
a fuel oil and/or improving the oxidation of carbonaceous products derived
from the
combustion or pyrolysis of a fuel oil, which process comprises adding to the
fuel oil before
combustion or pyrolysis thereof an additive composition as defined in the
first aspect or
second aspect.
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In a further aspect, the present invention provides the use of an additive
composition, as
defined in the first aspect or second aspect, in a fuel oil to improve the
combustion of the
fuel oil and/or to improve the oxidation of carbonaceous products derived from
the
combustion or pyrolysis of the fuel oil.
Treatment with the metal compounds of the present invention in such an amount
that the
total metal in the fuel oil composition is at most 50 ppm, such as 2 to 50
ppm, by mass
based on metal may also prove to be effective in improving fuel lubricity, as
measured in
tests such as the HFRR (High Frequency Reciprocating Rig) test.
Accordingly, an aspect of the present invention provides for a process for
improving
lubricity performance of a fuel oil containing at most 0.05 mass % of sulfur
which
comprises adding to the fuel oil an additive composition as defined in the
first aspect in
such an amount that the metal content derived from (a) and (b) in the
resulting fuel oil
composition is at most 50 ppm by mass.
Another aspect of the present invention provides the use of an additive
composition, as
defined in the first aspect, in a fuel oil containing at most 0.05 mass % of
sulfur in such an
amount that the metal content derived from (a) and (b) in the resulting fuel
oil composition
is at most 50 ppm by mass, to improve the lubricity performance of the fuel
oil.
Surprisingly, it has been found that the defined metal compounds of the
present invention
provide fuel oil, particularly diesel fuel oil and heating oil, compositions
with improved
low temperature flow performance compared to fuel oil compositions comprising
the
alkaline earth metal compounds alone, such as a neutral calcium compound. This
effect is
particularly apparent in the Cold Filter Plugging Point (CFPP) test (according
to IP 309/96)
or the Simulated Filter Plugging Point (SFPP) test (according to IP 419/96).
Further, the defined metal compounds of the present invention when added to
fuel oil, such
as diesel fuel oil or heating oil, provide the resulting compositions with
better stability
against water, thereby minimising the formation of emulsions in the fuel oil
compositions.
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The haze forming tendencies of a fuel oil composition may be measured
according to
ASTM D 1094.
