U.S. patent application number 12/162585 was filed with the patent office on 2009-10-01 for lubricant compositions comprising colloidal dispersions of rare earth compounds and catalytic combustion of engine exhaust soots therewith.
This patent application is currently assigned to Rhodia Operations. Invention is credited to Gilbert Blanchard, Virginie Harle, Claire Pitois, Stephan Verdier.
Application Number | 20090241523 12/162585 |
Document ID | / |
Family ID | 36589232 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090241523 |
Kind Code |
A1 |
Harle; Virginie ; et
al. |
October 1, 2009 |
LUBRICANT COMPOSITIONS COMPRISING COLLOIDAL DISPERSIONS OF RARE
EARTH COMPOUNDS AND CATALYTIC COMBUSTION OF ENGINE EXHAUST SOOTS
THEREWITH
Abstract
Engines equipped with an exhaust line fitted with a particulate
filter, in which the particulates contained in the exhaust gas are
trapped on such filter, and wherein the trapped particulates are
periodically burned off, are operated by improvedly catalyzing the
combustion of said particles utilizing a composition containing
mixture of a lubricating oil and a colloidal dispersion as the
engine-lubricating composition, which dispersion includes particles
of at least one compound of at least one rare earth and an
amphiphilic agent.
Inventors: |
Harle; Virginie; (Senlis,
FR) ; Verdier; Stephan; (Lyon, FR) ; Pitois;
Claire; (Sunbyberg, SE) ; Blanchard; Gilbert;
(Lagny-le-sec, FR) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Rhodia Operations
Aubervilliers
FR
|
Family ID: |
36589232 |
Appl. No.: |
12/162585 |
Filed: |
January 18, 2007 |
PCT Filed: |
January 18, 2007 |
PCT NO: |
PCT/EP2007/050493 |
371 Date: |
December 11, 2008 |
Current U.S.
Class: |
60/297 ; 508/154;
508/171; 60/299 |
Current CPC
Class: |
C10N 2030/50 20200501;
C10N 2030/38 20200501; C10M 141/02 20130101; C10N 2010/06 20130101;
C10M 141/10 20130101; F01N 3/023 20130101; C10M 2201/041 20130101;
C10M 2207/126 20130101; C10M 141/08 20130101; C10M 2223/04
20130101; C10M 2203/102 20130101; C10M 2225/00 20130101; C10M
2203/022 20130101; C10M 2223/06 20130101; C10N 2050/01 20200501;
C10M 2201/062 20130101; C10M 2203/06 20130101; C10M 2203/104
20130101; C10N 2010/14 20130101; C10M 2203/02 20130101; C10M
2219/044 20130101 |
Class at
Publication: |
60/297 ; 508/154;
508/171; 60/299 |
International
Class: |
F01N 3/035 20060101
F01N003/035; C10M 169/04 20060101 C10M169/04; C10M 125/10 20060101
C10M125/10; F01N 3/10 20060101 F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2006 |
FR |
0600838 |
Claims
1.-12. (canceled)
13. A method for operating an engine producing exhaust gases that
contain particulates and equipped with a muffler provided with a
particulate filter, in which the particulates are trapped on said
filter and the catalytic combustion of the trapped particulates is
carried out periodically, wherein, to assist catalyzing the
combustion of said particulates, a lubricant composition which
comprises admixture of: a lubricating oil; and a colloidal
dispersion of particles of at least one compound of at least one
rare earth and an amphiphilic agent which at least partially
interacts therewith, is provided for said engine.
14. The method as defined by claim 13, wherein said at least one
rare earth is selected from the group consisting of cerium,
lanthanum, yttrium, neodymium, gadolinium and praseodymium.
15. The method as defined by claim 13, wherein the colloidal
dispersion comprises particles of a compound of iron and of a rare
earth.
16. The method as defined by claim 13, said amphiphilic agent
comprising an acid.
17. The method as defined by claim 16, said acid comprising a
carboxylic acid having from 10 to 60 carbon atoms.
18. The method as defined by claim 16, said acid being selected
from the group consisting of fatty acids of tall oil, of soybean
oil, of tallow or of linseed oil, oleic acid, linoleic acid,
stearic acid and isomers thereof, pelargonic acid, capric acid,
lauric acid, myristic acid, dodecylbenzenesulfonic acid,
2-ethylhexanoic acid, naphthenic acid, hexoic acid, toluenesulfonic
acid, toluenephosphonic acid, laurylsulfonic acid, laurylphosphonic
acid, palmitylsulfonic acid and palmitylphosphonic acid.
19. The method as defined by claim 13, wherein the colloidal
dispersion comprises particles of at least one compound of at least
one rare earth, at least 90% of such particles being single-crystal
particles.
20. The method as defined by claim 19, wherein the particles have a
D.sub.50 value ranging from 1 to 5 nm
21. The method as defined by claim 13, wherein the content of rare
earth, optionally of rare earth and of iron, expressed as metal
element, comprising the colloidal dispersion in the lubricating
composition, is at most 15% by weight of the total weight
thereof.
22. The method as defined by claim 13, utilizing a lubricant
composition which comprises the lubricating oil and the colloidal
dispersion prepared prior to providing same in the engine.
23. The method as defined by claim 13, wherein the engine is a
diesel engine or a petrol engine.
24. The method as defined by claim 13, carried out employing an
engine operating with a fuel which contains a catalyst for
combustion of the particulates or with an engine equipped with a
muffler which comprises a catalytic particulate filter.
25. A lubricant composition which comprises admixture of: a
lubricating oil; and a colloidal dispersion of particles of at
least one compound of at least one rare earth and an amphiphilic
agent which at least partially interacts therewith.
26. The lubricant composition as defined by claim 25, said
amphiphilic agent comprising an acid.
27. The lubricant composition as defined by claim 25, said
colloidal dispersion comprising particles of at least one cerium
compound.
28. The lubricant composition as defined by claim 27, said
colloidal dispersion optionally comprising particles of another
rare earth and of iron.
29. The lubricant composition as defined by claim 28, said
colloidal dispersion comprising particles of a mixed oxide and/or a
hydrated mixed oxide.
30. The lubricant composition as defined by claim 25, said
colloidal dispersion comprising particles of at least one compound
of at least one rare earth elected from the group consisting of
cerium, lanthanum, yttrium, neodymium, gadolinium and
praseodymium.
31. The lubricant composition as defined by claim 25, said
colloidal particles comprising a complexing agent.
32. The lubricant composition as defined by claim 25, said
colloidal particles being suspended in an organic liquid phase.
33. An internal combustion engine oil comprising the lubricant
composition as defined by claim 25.
Description
[0001] The present invention relates to a method of operating an
engine using a lubricating composition comprising a colloidal
dispersion of a rare earth to catalyze the combustion of soot.
[0002] It is known that during the combustion of diesel fuel in a
diesel engine, the carbonated products have a tendency to form
soot, which is reputedly harmful both for the environment and for
the health. Techniques have long been sought that make it possible
to reduce the emission of this soot or carbonated particulates. The
same problem is faced for petrol engines that operate in lean burn
mode (lean-burn engines) which themselves also emit such
particulates.
[0003] One satisfactory solution that is now widely used consists
in collecting the particulates on a filter which is regularly
regenerated to prevent it from clogging up. The regeneration of the
filter is facilitated even more when the auto-ignition temperature
of the soot is low which may be obtained by introducing a catalyst
into the very heart of the soot during the combustion. This
technology, known under the name "Fuel-Borne Catalysis" or FBC is
also widely used. The thus additivated soot has an auto-ignition
temperature that is low enough to be frequently attained during
normal running of the engine or during specific regeneration
cycles.
[0004] Although the FBC technology is satisfactory, there is
however a need for other alternative technologies so as to be able
to have the widest possible range of solutions and to thus be able
to solve the problem of reducing the emission of harmful
particulates regardless of the conditions under which this problem
is faced.
[0005] The object of the invention is therefore to provide one such
novel technology.
[0006] For this purpose, the invention relates to a method of
operating an engine capable of producing exhaust gases that contain
particulates and equipped with a muffler provided with a
particulate filter, in which the particulates are trapped on said
filter and the combustion of the trapped particulates is carried
out periodically and which is characterized in that, with a view to
catalyzing the combustion of said particulates, use of made, as a
lubricating composition for the engine, of a composition which
results from the mixture of: [0007] a lubricating oil; and [0008] a
colloidal dispersion which comprises particles of a compound of at
least one rare earth and an amphiphilic agent.
[0009] The method of the invention has the advantage of doing away
with the presence of a specific tank for the soot combustion
catalyst and of a device for metering this catalyst into the fuel,
unlike the method using FBC technology.
[0010] Other features, details and advantages of the invention will
appear more completely still on reading the description which
follows, and also various concrete but non-limiting examples
intended to illustrate it.
[0011] The expression "rare earth" is understood to mean, in this
same description, the elements of the group composed of yttrium,
scandium and the elements from the Periodic Table having an atomic
number between 57 and 71 inclusive.
[0012] The composition of the invention results from a mixture of
two essential components: the lubricating oil and the colloidal
dispersion.
[0013] Lubricating oils are well known to a person skilled in the
art. It may be recalled that these products contain a base oil
having a lubricating property. This base oil may be a mineral oil
derived from petroleum, especially based on paraffins, aromatics or
isoparaffins and mixtures of these compounds. The mineral oil may
be obtained by vacuum distillation of a crude oil, the distillate
obtained is then hydrocracked, hydrotreated and subsequently
dewaxed and/or hydroisomerized so as to improve the properties such
as the viscosity and those of the flow of the base oil thus
obtained.
[0014] These base oils may also be synthesis oils based on
polyalphaolefins or organic esters.
[0015] The viscosity index of the mineral oils may be, for example,
between 90 and 100 (index measured according to the ASTM D2270
standard), that of the hydrotreated products between 120 and 130
and this index may be greater than 140 for synthetic oils based on
polyalphaolefins and may even reach 200 for those based on organic
esters.
[0016] Also in a known manner, the lubricating oils additionally
contain various additives that can be classified into three groups:
those intended to improve the chemical stability of the oil or to
inhibit the effects of degradation products, those which improve
the rheological properties and those which protect metallic
surfaces and have a wear-resistant effect.
[0017] Found in the first group are antioxidant additives based,
for example, on phenols, on substituted arylamines or on
sulfur-containing compounds or also on zinc
dialkyldithiophosphates. Also found are detergent additives of the
type of salts of organic acids or of phenols or of divalent metals
and dispersant additives of the organic surfactant type.
[0018] The additives of the second group are those which act on the
pour point of the oils and are of the type of oligomers having
alkyl chains or else the products known as antifreeze products of
the alkylnaphthalene type, long-chain polyalcohol acrylates, or
else of the alkylated polystyrene type. Also found in this second
group are additives that improve the viscosity index. These
additives are based on hydrocarbon-based polymers (for example,
ethylene/propylene copolymers) or on polymers having an ester
functional group (of polymethacrylate type). Finally, also found in
this second group of additives are anti-foaming products, for
example based on silicones.
[0019] The third group of additives comprises products with a
wear-resistant effect. These are generally organic products
containing sulfur, chlorine or phosphorus of the type of
dithiophosphoric derivatives or phosphomolybdate derivatives.
[0020] The second main component of the composition of the
invention is the colloidal dispersion.
[0021] The expression "colloidal dispersion" denotes, in the
present description, any system composed of fine solid particles of
colloidal dimensions based on a compound of a rare earth, in
suspension in a liquid phase, said particles possibly, in addition,
optionally containing residual amounts of bonded or adsorbed ions
such as, for example, nitrates, acetates, citrates or ammoniums.
The expression "colloidal dimensions" is understood to mean
dimensions between around 1 nm and around 500 nm.
[0022] The particles may more particularly have an average size of
at most about 250 nm, especially of at most 100 nm, preferably of
at most 20 nm and more preferably still of at most 15 nm. It will
be noted that in such dispersions, the rare-earth compound may be,
preferably, completely in the form of colloids, or in the form of
colloids and partially in the form of ions.
[0023] The particle size distribution, of which mention is made
above and for the remainder of the description, except where
indicated otherwise, is determined by transmission electron
microscopy (TEM), conventionally, on a sample that has first been
dried and deposited on a carbon membrane supported on a copper
grid.
[0024] The rare earth may be chosen, more particularly, from
cerium, lanthanum, yttrium, neodymium, gadolinium or praseodymium.
Cerium may most particularly be chosen.
[0025] According to a first variant of the invention, the colloidal
dispersion is characterized in that it comprises particles of a
compound of cerium and of another rare earth.
[0026] According to another variant, the colloidal dispersion of
the invention is characterized in that it comprises particles based
on a compound of cerium, optionally of another rare earth and of
iron.
[0027] More particularly, when the particles of the dispersion of
the invention are based on a compound of several elements, that is
to say cerium, another rare earth and/or iron, these elements are
in a mixture within each particle, these elements generally being
in the form of mixed oxides and/or hydrated mixed oxides
(oxyhydroxides).
[0028] In the case of a colloidal dispersion of cerium, this
element is preferably mainly in the form of cerium IV. For example,
the content of cerium III relative to cerium IV (content expressed
by the Ce III/total Ce atomic ratio) is generally at most 40%. It
may vary as a function of the embodiments of the dispersions used
and may thus be at most 20%, more particularly at most 10%, and
more particularly still at most 1%.
[0029] In the case of the aforementioned first variant, the rare
earth other than cerium may more particularly be lanthanum or
praseodymium. Of course, the present invention covers the case
where the particle is a compound of cerium and of several other
rare earths in combination.
[0030] The proportion of the rare earth other than cerium is
preferably at least 10%, more particularly at least 20%, and more
particularly still at most 50%, in moles relative to the total
number of moles of cerium and of rare earth expressed as oxide.
[0031] In the case of the second variant, the proportion of cerium
is preferably at most 50%, more particularly at most 20% and more
particularly still at most 10%, this proportion being expressed in
moles of cerium oxide CeO.sub.2 relative to the total number of
moles of cerium oxide and of iron oxide Fe.sub.2O.sub.3.
[0032] The two variants may be combined, that is to say that the
particles may be compounds of cerium, of at least one other rare
earth and of iron.
[0033] As indicated above, the particles of the colloidal
dispersion are in suspension in a liquid phase which here is an
organic phase.
[0034] This organic phase may be composed of the base oil having a
lubricating property described above or it may also be a mixture of
this base oil with another organic phase, miscible with this oil.
Specifically and as will be seen later on, the lubricating
composition of the invention may be obtained by mixing the
lubricating oil with a previously prepared colloidal dispersion. In
this case, this dispersion comprises an organic phase which may be
a hydrocarbon, more particularly an apolar hydrocarbon.
[0035] By way of example of an organic phase, mention may be made
of the aliphatic hydrocarbons such as hexane, heptane, octane,
nonane, inert cycloaliphatic hydrocarbons such as cyclohexane,
cyclopentane and cycloheptane, aromatic hydrocarbons such as
benzene, toluene, ethylbenzene, xylenes and liquid naphthenes. Also
suitable are oil cuts of the ISOPAR or SOLVESSO type (trade marks
of Exxon), especially SOLVESSO 100 which mainly contains a mixture
of methylethylbenzene and trimethylbenzene, SOLVESSO 150 which
contains a mixture of alkylbenzenes, in particular of
dimethylbenzene and tetramethylbenzene and ISOPAR which mainly
contains C-11 and C12 isoparaffinic and cycloparaffinic
hydrocarbons. Mention may also be made, as other oil cuts, of those
of the PETROLINK.RTM. type from Petrolink or of the ISANE.RTM. type
from Total.
[0036] Use may also be made, for the organic phase, of chlorinated
hydrocarbons such as chlorobenzene or dichlorobenzene, or
chlorotoluene. Ethers and also aliphatic and cycloaliphatic ketones
such as, for example, diisopropyl ether, dibutyl ether, methyl
ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and mesityl
oxide, may be envisioned.
[0037] Esters may be envisioned, but they have the drawback of
risking being hydrolyzed. Mention may be made, as esters capable of
being used, of those derived from the reaction of acids with C1 to
C8 alcohols and especially the palmitates of secondary alcohols
such as isopropanol. Mention may be made of butyl acetate by way of
example.
[0038] Of course, the organic phase may be based on a mixture of
two or more hydrocarbons or compounds of the type described
above.
[0039] Finally, as indicated above, the choice of the organic phase
from the examples which have just been given will be made depending
on its compatibility or miscibility with the lubricating oil.
[0040] Furthermore, the colloidal dispersion comprises an
amphiphilic agent.
[0041] This amphiphilic agent at least partly interacts, either via
grafting, or via electrostatic bonding, with the particles of the
rare earth and, optionally, iron compound.
[0042] This agent may more particularly be an acid.
[0043] The acid is more particularly chosen from organic acids
which comprise at least 6 carbon atoms, more particularly still
from 10 to 60 carbon atoms, preferably from 10 to 50 carbon atoms
and more preferably still from 15 to 25 carbon atoms.
[0044] These acids may be linear or branched. They may be aryl,
aliphatic or arylaliphatic acids, optionally bearing other
functional groups on condition that these functional groups are
stable in the media where it is desired to use the dispersions
according to the present invention. Thus, use may be made, for
example, of aliphatic carboxylic acids, aliphatic sulfonic acids,
aliphatic phosphonic acids, alkoylarylphosphonic acids and
alkoylarylsulfonic acids that have around 10 to around 40 carbon
atoms, which are natural or synthetic. It is of course possible to
use the acids as a mixture.
[0045] It is also possible to use carboxylic acids where the
carbon-based chain bears ketone functional groups such as pyruvic
acids substituted at the alpha position with the ketone functional
group. These may also be .alpha.-halo-carboxylic acids or
.alpha.-hydroxycarboxylic acids. The chain attached to the
carboxylic group may bear unsaturations. The chain may be
interrupted by ether or ester functional groups on condition that
the lipophilicity of the chain bearing the carboxylic group is not
impaired too much.
[0046] By way of example, mention may be made of the fatty acids of
tall oil, of soybean oil, of tallow or of linseed oil, oleic acid,
linoleic acid, stearic acid and isomers thereof, pelargonic acid,
capric acid, lauric acid, myristic acid, dodecylbenzenesulfonic
acid, 2-ethylhexanoic acid, naphthenic acid, hexoic acid,
toluenesulfonic acid, toluenephosphonic acid, laurylsulfonic acid,
laurylphosphonic acid, palmityl-sulfonic acid and
palmitylphosphonic acid.
[0047] As an amphiphilic agent, mention may also be made of
polyoxyethylenated alkyl ether phosphates. These are understood
here to be organophosphates of formula:
##STR00001##
or else polyoxyethylenated dialkoyl phosphates of formula:
##STR00002##
in which: [0048] R.sup.1, R.sup.2, R.sup.3, which are identical or
different, represent a linear or branched alkyl radical, especially
having 2 to 20 carbon atoms; a phenyl radical; an alkylaryl
radical, more particularly an alkylphenyl radical, especially with
an alkyl chain having 8 to 12 carbon atoms; an arylalkyl radical,
more particularly a phenylaryl radical; [0049] n is the number of
ethylene oxide units which may range from 0 to 12 for example; and
[0050] M represents a hydrogen, sodium or potassium atom.
[0051] The radical R.sup.1 may especially be a hexyl, octyl, decyl,
dodecyl, oleyl or nonylphenyl radical.
[0052] Mention may be made, as an example of this type of
amphiphilic compounds, of those sold under the trade marks
LUBROPHOS.RTM. and RHODAFAC.RTM. sold by Rhodia and especially the
products below: [0053] the RHODAFAC.RTM. RA 600 polyoxyethylene
(C8-C10) alkyl ether phosphates; [0054] the RHODAFAC.RTM. RS 710 or
RS 410 polyoxyethylene tridecyl ether phosphate; [0055] the
RHODAFAC.RTM. PA 35 polyoxyethylene oleocetyl ether phosphate;
[0056] the RHODAFAC.RTM. PA 17 polyoxyethylene nonylphenyl ether
phosphate; and [0057] the RHODAFAC.RTM. RE 610 polyoxyethylene
(branched)nonyl ether phosphate.
[0058] The amount of amphiphilic agent present in the dispersion
may be defined by the molar ratio r:
r=number of moles of amphiphilic agent/number of moles of compound
E E here denoting the rare earth or rare earths or the combination
of rare earth(s) and iron.
[0059] This molar ratio may be between 0.2 and 1, preferably
between 0.4 and 0.8.
[0060] The dispersion that can be used in the method of the
invention may be according to one specific embodiment.
[0061] According to this embodiment, the dispersion is such that at
least 90% of the particles are single-crystal particles. The
expression "single-crystal particles" is understood to mean
particles which, when the dispersion is examined by TEM
(high-resolution transmission electron microscopy), appear
individualized and composed of a single crystallite.
[0062] The cryo-TEM technique may also be used to determine the
aggregation state of the elementary particles. This technique makes
it possible to observe, via transmission electron microscopy (TEM),
samples that are kept frozen in their natural medium which is
either water or organic diluents such as aromatic or aliphatic
solvents such as, for example, SOLVESSO and ISOPAR or else certain
alcohols such as ethanol.
[0063] Freezing is carried out on thin films of around to 50 100 nm
in thickness either in liquid ethane for aqueous samples or in
liquid nitrogen for others.
[0064] With cryo-TEM, the dispersion state of the particles is well
preserved and representative of that present in the actual
medium.
[0065] According to this embodiment, the particles have a fine and
narrow particle size distribution. Specifically, they have a
D.sub.50 between 1 and 5 nm, preferably between 2 and 3 nm.
[0066] Generally, and by way of example only, the concentration of
the dispersion of rare earth, and optionally of iron, is between 1
and 40% by weight of oxide(s) of rare earth(s) or of oxide(s) of
rare earth(s) and of iron Fe.sub.2O.sub.3 relative to the total
weight of the dispersion.
[0067] Finally, generally and by way of example for the colloidal
dispersions of a compound of a rare earth, optionally of a rare
earth and of iron and preparation thereof, reference may be made to
the whole of the description of each of Patent Applications EP 0
671 205, WO 01/10545 and WO 97/19022.
[0068] The lubricating composition that can be used in the method
of the invention may be prepared by mixing a lubricating oil with a
colloidal dispersion of a rare-earth compound or of a rare-earth
and iron compound. This mixing may be carried out in proportions
which are not critical and which may vary over a wide range. By way
of example, these proportions may be such that the content of rare
earth, optionally of rare earth and of iron, in the lubricating
composition, expressed as metal element, and originating from the
colloidal dispersion is at most 15% by weight of the total
composition, more particularly at most 10%, proportions of a few
percent only being possible.
[0069] It is observed that the composition thus obtained is stable,
that is to say that no settling of the dispersion and therefore no
deposition of the cerium or iron particles at the bottom of the
tank containing the lubricating composition is observed.
Furthermore, this stability is maintained even when the lubricating
composition is exposed to a high temperature, which is the case
during the operation of the engine for which the composition is
used as a lubricant. Moreover, it is unexpectedly observed that the
use of this composition in the operation of the engine definitely
leads to a catalysis of the combustion of soot.
[0070] The method of the invention applies to an engine which,
during its operation, is capable of producing harmful particulates,
such as soot, which are found in the exhaust gases. It may more
particularly be a diesel or a petrol engine operating in lean burn
mode.
[0071] This method applies to an engine which, in a known manner,
is equipped with an exhaust line or muffler, integrated into which
is a particulate filter. Conventionally, this filter comprises a
filter of the type having a filtering wall made of ceramic or made
of silicon carbide through which the exhaust gases circulate.
However, it may also be one or more screens made of wire mesh or
else a foam-type filter made of ceramic or made of fibrous
material.
[0072] The method of the invention aims to catalyze the combustion
of the particulates or soot trapped on the particulate filter. In
the case of the invention, the rare-earth or iron and rare-earth
compound is used as a catalyst for the combustion of this soot and
it is conveyed by the lubricating composition and not by the fuel
as in the methods of the prior art. The lubricating composition,
prepared prior to its use in the engine and therefore comprising
the dispersion of rare earth or of iron and rare earth, is
introduced into the oil reservoir of the engine, for example during
an oil change. The lubricating composition thus passes into the
lubricating circuit of the engine. It is observed that the
rare-earth or rare-earth and iron compound introduced by the
lubricating composition is found in the soot and may thus help to
catalyze the combustion thereof.
[0073] Of course, it is possible, without departing from the scope
of the present invention, to implement the above method while
using, for the operation of the engine, a fuel which furthermore
contains a catalyst for the combustion of the soot. This catalyst
may also be a colloidal dispersion such as described above. It is
similarly possible to implement the method of the invention in a
system in which the muffler is equipped with a catalyzed
particulate filter. This type of filter is well known, it is a
filter in which, during its manufacture, a catalyst for the
oxidation of particulates or soot is incorporated.
[0074] Examples will now be given.
EXAMPLE 1
[0075] This example relates to the preparation of a lubricating
composition that can be used in a method according to the
invention.
[0076] For this preparation, use was made of a colloidal dispersion
based on cerium prepared according to a method of the type of that
from Example 4 of Patent Application EP 671 205, hut with a
temperature of 160.degree. C. for the autoclave treatment. The
organic phase of this dispersion was ISOPAR and the amphiphilic
agent was isostearic acid. The content of ceric nitrate used was
adjusted so as to obtain a colloidal dispersion containing 25% by
weight of metal cerium. The colloids had an average size of 5
nm.
[0077] Added to this dispersion was a commercial oil (Total Activa
Diesel 10W40) so as to obtain a lubricating composition containing
43% by weight of this commercial oil and 57% by weight of the
colloidal dispersion.
EXAMPLE 2
[0078] This example relates to the preparation of a second
lubricating composition that can be used in a method according to
the invention.
[0079] For this preparation, use was made of a colloidal dispersion
based on cerium and on iron in a molar proportion of metal of
50/50, prepared according to a method of the type from Example 3 of
Patent Application WO 01/10545. The organic phase of this
dispersion was ISOPAR and the amphiphilic agent was isostearic
acid. The dispersion contained 10% by weight of metal (cerium and
iron). The colloids had a size between 3 and 4 nm and were
perfectly individualized.
[0080] Added to this dispersion was a commercial oil (Total Activa
Diesel 10W40) so as to obtain a lubricating composition containing
28% by weight of this commercial oil and 72% by weight of the
colloidal dispersion.
EXAMPLE 3
[0081] This example relates to a test for catalytic oxidation of
the soot carried out in the presence of a lubricating composition
that can be used in a method according to the invention. The
catalytic soot oxidation properties were measured by
thermogravimetric analysis. A Setaram thermohalance equipped with a
quartz boat, in which a specimen containing around 20 mg of sample
was placed, was used.
[0082] The sample was composed of a mixture of 20% by weight of the
lubricating composition from Example 1 and 80% by weight of carbon
black. The carbon black used to simulate the soot emitted by a
diesel engine was the carbon black sold by Cabot under the
reference ELFTEX 125. The lubricating composition and carbon black
mixture was homogenized by mixing with a spatula. The paste thus
obtained was first dried in a ventilated oven at 60.degree. C. then
at 120.degree. C.
[0083] 20 mg of the sample thus prepared and treated were
introduced into the boat of the thermobalance, then a gas stream
composed of an air/water mixture in respective volume proportions
of 87% and 13% was circulated. After a hold of 30 minutes at
150.degree. C., the temperature rise up to 900.degree. C. was
started with a ramp of 10.degree. C./min and the mass loss of the
sample was recorded as a function of the temperature.
EXAMPLE 4
[0084] This example was carried out according to the same procedure
as Example 3 but with the lubricating composition described in
Example 2.
COMPARATIVE EXAMPLE 5
[0085] This example relates to a soot oxidation test carried out in
the presence of a lubricating composition from the prior art. The
test was carried out according to the same procedure but using the
pure commercial oil Total Activa Diesel 10W40. The sample thus
evaluated was therefore composed of a mixture of 20% by weight of
the pure commercial oil and 80% by weight of carbon black.
[0086] The results are given in table 1: they are expressed as the
half-oxidation temperature of the soot (T50% (soot)) corresponding
to the temperature required to obtain half of the mass loss
measured between 200.degree. C. and 900.degree. C.
TABLE-US-00001 TABLE 1 Example T50% (soot) in .degree. C. 3
510.degree. C. 4 615.degree. C. 5 Comparative 610.degree. C. Soot
alone 620.degree. C.
[0087] It is observed that the addition of pure commercial oil has
no or little effect on the half-conversion temperature of the soot,
whereas the use of a lubricating composition containing a
commercial oil and a colloidal dispersion containing cerium or
cerium and iron makes it possible to very significantly reduce the
combustion temperature of the soot.
EXAMPLE 6
[0088] In this example the colloidal dispersion of cerium and of
iron from Example 2 was taken again and 10 g of this dispersion
containing 10% by weight of metal cerium and metal iron were added
to 160 g of an engine oil (Elf Prestigrade 15W40) so as to obtain a
lubricating composition containing 94% by weight of this commercial
oil and 6% by weight of the commercial colloidal dispersion. The
content of metal iron of this lubricating composition was thus
0.20% by weight, whereas that of metal cerium was 0.45% by
weight.
[0089] This lubricating composition was then introduced into a
partially stoppered container, that was itself placed in a
ventilated chamber kept at 110.degree. C. The iron and cerium
content of the composition was then regularly measured in the upper
part of the container via a chemical metering technique (ICP).
[0090] Table 2 below gives the iron and cerium contents thus
measured after various residence times in the chamber at
110.degree. C.
TABLE-US-00002 TABLE 2 Heating time at 110.degree. C. in days wt %
cerium wt % iron 0 0.45 0.20 1 0.45 0.20 3 0.45 0.20 6 0.45 0.20 10
0.45 0.20 13 0.45 0.20 17 0.45 0.20 28 0.45 0.20 38 0.45 0.20 55
0.45 0.20 79 0.45 0.20
[0091] It is therefore observed that the thermal stability of this
lubricating composition is very high considering that the iron and
cerium contents do not change over 79 days of continuous heating at
110.degree. C. This stability time determined under these
conditions may be considered as sufficient to ensure the stability
of the lubricating composition between two oil changes of the
engine oil circuit.
* * * * *