Fuel and related compositions – Liquid fuels – Aluminum or heavy metal – other than lead – containing
Reexamination Certificate
1999-09-22
2001-04-03
Lovering, Richard D. (Department: 1712)
Fuel and related compositions
Liquid fuels
Aluminum or heavy metal, other than lead, containing
C423S263000, C516S033000
Reexamination Certificate
active
06210451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to novel colloidal organic sols comprising tetravalent metal oxide/organic acid complexes, in particular those of cerium oxide, and, more especially, to such organic sols having great stability and controlled particle size.
2. Description of the Prior Art
Colloidal suspensions in organic media of micrometric or submicronic particles are known to this art, the properties of these colloidal suspensions being similar to those of pure solutions. These colloidal suspensions are generally designated by the term “sols.”
These sols had the property either of being stable with time and being of coarse particle size (in general, hydrodynamic diameter on the order of one micrometer and high viscosity), or being of fine particle size but of low stability: half-life duration at most equal to one or two months, and of relatively low concentration. However, to date, as far as is known these properties have not been simultaneously obtained.
For certain applications, the aforesaid properties are essential. More particularly for the reasons hereinbelow outlined, the use of the sols as additives for fuels for internal combustion engines requires both the option of existing in a high concentration and the necessity of having a low particle size and a very high stability.
The use of the sols as additives for diesel engines is a representative example of the constraints to which such a sol must comply.
During the burning of diesel fuel in diesel engines, the carbon-containing products of combustion have a tendency to form soots which are considered harmful both to the environment and to human health. It has long been sought to reduce the emission of these carbon-containing particles, hereinafter sometimes referred to simply as “soots.” The research in this area takes account of the necessity of not increasing the emission of carbon monoxide and of gases which are considered toxic and mutagenic, such as nitrogen oxides.
A great many solutions have been proposed for reducing these carbon-containing emissions.
However, attention is increasingly focused on fitting the exhaust systems of internal combustion engines with a filter capable of trapping all, or a very high proportion (at least 80% by mass) of the carbon-containing particles generated by the combustion of the various fuels. This technique is, however, limited by the storage capacity of the filter (or trap); it is necessary either to empty the filter or to incinerate the soots contained therein. This operation, known as regeneration, is extremely expensive and difficult to implement. One of the most commonly proposed solutions is the combustion of these soots, which combustion is intermittently carried out either by electrical heating or by use of a fossil igniter fuel.
Nonetheless, this technique presents many disadvantages, not the least of which is the risk of thermal shock leading to fracturing or cracking of the ceramic filter, or to melting of the metal filter.
One solution which would be satisfactory entails introducing catalysts into the soots which make possible frequent self-ignition of the soots collected in the filter. To accomplish this, it is necessary for these soots to have a self-ignition temperature which is sufficiently low to be frequently attained during normal operation of the engine.
SUMMARY OF THE INVENTION
It has now been determined that cerium is a valuable element for reducing the self- or auto-ignition temperature of the soots.
However, in order to be conveniently used and in order to comply with the provisions of various governmental regulations, the additives must be introduced as required from a tank which need be replaced only every 50,000 kilometers. Under these conditions, the additives must be both very concentrated and sufficiently stable as not to be detrimentally affected by the agitation promoted by operation of the vehicle and by the interval of several years between replacements.
Accordingly, a major object of the present invention is the provision of novel colloidal organic sols well suited for catalyzing the auto-ignition of soot particles, which are both very concentrated and very stable, not only when concentrated but also when diluted, and which comprise tetravalent metal oxide/organic acid complexes.
Another object of the present invention is the provision of novel colloidal organic sols which after introduction into a diesel fuel and then after combustion of same, imparts good self-ignition of the resulting soots.
Briefly, the present invention features colloidal organic sols which comprise (a) particles of a tetravalent metal oxide, (b) an amphiphilic acid system, and (c) a diluent therefor, said particles (a) having a d
90
which is not greater than 200 nanometers and said sols exhibiting at least one of the following characteristics, (1) said particles of tetravalent metal oxide comprise agglomerates of crystallites, advantageously of cerium dioxide, in which crystallites the d
80
, advantageously the d
90
, measured by photometric counting (high resolution transmission electron microscopy) is not greater than 5 nanometers, ninety percent (by mass) of the agglomerates comprising from 1 to 5 and preferably from 1 to 3 crystallites, and/or (2) said amphiphilic acid system (b) comprising at least one organic acid containing 11 to 50 carbon atoms having at least one branch in the &agr;-, &bgr;-, &ggr;- or &dgr;-position to the atom bearing the acidic hydrogen.
DETAILED DESCRIPTION OF BEST MODE AND PREFERRED EMBODIMENTS OF THE INVENTION
More particularly according to the present invention, the most preferred sols are those having one of the characteristics (1) and (2), in toto, and at least partially satisfy the other.
In a first embodiment of the invention, it is possible to be less restrictive as regards the amphiphilic acids on condition of being more restrictive as regards the particle size conditions. Herein, the particle size characteristics are often notations of the d
n
type where n is a number ranging from 1 to 99. This notation is well known to many arts, but, as it is somewhat rarer in chemistry, it will now be defined. This notation represents the particle size such that n % (by weight, or more exactly by mass, since the weight is not an amount of matter but a force) of the particles is less than or equal to said size. These more restrictive conditions and the manner of responding thereto are explained below. Advantageously, at least 50% (statistical value) by mass of the agglomerates are monocrystalline, namely, they comprise only a single crystallite (or at least appear to consist only of a single crystallite when the sol is examined by HRTEM (High Resolution Transmission Electron Microscopy)).
In addition, it is possible, by varying the technique and the conditions of hydrolysis, to ensure that 80%, preferably 90%, by mass of the crystallites are of a size less than a predetermined value within the range 2 to 5 nanometers and preferably 3 to 4 nanometers.
The molar ratio of the amphiphilic acid to the metal elements of the sol is advantageously not greater than 0.5, advantageously not greater than 0.4 and preferably not greater than 0.3. In this instance, the molar ratio must be considered a functional molar ratio (namely, that mole of amphiphilic acid is the number of moles multiplied by the number n of useful acidic functional groups). More particularly, the number of acid equivalents represents the number of molecules of acid when the acid employed is monofunctional and it is necessary to double or triple this number in the event of diacids or triacids and, more generally, to multiply it by the number of acidic functional groups in the event of a polyacid.
It is desirable, in the sol, for the residual cerium(III) content with respect to cerium(IV) to be as low as possible, typically less than 1.5% and advantageously not greater than 1% and preferably not greater than ½%.
The sol advantageously has a concentration such that the cerium dioxide content (with accompanying impurities) contained
Chopin Thierry
Macaudiere Pierre
Touret Olivier
Burns Doane Swecker & Mathis L.L.P.
Lovering Richard D.
Rhone-Poulenc Chimie
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