Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1999-10-05
2002-06-25
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S110000, C502S132000, C502S154000, C526S124300, C526S124500
Reexamination Certificate
active
06410475
ABSTRACT:
The present invention relates to a catalyst and more particularly to a catalyst intended for the polymerization of olefins comprising a solid catalytic composition, based on a transition metal, magnesium and halogen, deposited on an inorganic support. It also relates to a process for the manufacture of such catalysts. Finally, it relates to the use of the said catalyst, in combination with a cocatalyst of the type of the organometallic compounds, in the polymerization and the copolymerization of olefins and in particular of ethylene.
The use is known, in the low pressure polymerization of olefins and in particular of ethylene, of catalytic systems comprising a catalyst comprising a transition metal, magnesium and halogen, (so-called Ziegler-Natta, catalysts) and a cocatalyst of the type of the organometallic compounds of metals from Groups 1, 2, 12, 13, and 14 the Periodic Table. These known catalytic systems have very major advantages, such as a very high activity and a very high productivity. They are extremely simple to prepare and their preparation does not result in any polluting byproduct. Finally, their morphology makes possible continuous suspension polymerization, with a very high relative content of polymer and thus a very low relative amount of diluent to be treated before recycling. However, the polymers obtained as particles directly with their involvement, although with a consistent particle size, have a relatively low mean size for the particles.
In Patent Application WO-A-91/07443, it is recommended to impregnate an inorganic support by means of a solution of magnesium halide in a monocarboxylic acid alkyl ester and then, after drying, to treat the support in this order with an organometallic compound of a metal from Groups 1-13 (typically an alkylaluminium or a silicone compound) and finally with a compound of a transition metal.
Patent Application WO-A-91/09881 discloses the impregnation of a porous support made of inorganic oxide by means of a solution in an inert solvent of the reaction product of a magnesium compound, of a titanium compound and of an aluminium compound, followed by the removal of the solvent and then by a chlorination stage.
Patent Application WO-A-94/00498 discloses the manufacture of a catalytic composition obtained by bringing a support made of inorganic oxide, having a low content of surface hydroxyl groups, into contact with an impregnating solution comprising a magnesium compound, an alcohol and a tetravalent titanium compound and the subsequent chlorination of the support.
Silicon and aluminium oxides (silica and alumina), their mixtures and other silicates, and chromium, titanium and zirconium oxides appear among the inorganic supports generally envisaged in these documents, silica being in all cases particularly preferred and specifically disclosed, generally a silica pretreated for the purpose of removing the surface hydroxyl groups. The supported catalytic solids disclosed in these documents result in an increased activity with regard to the polymerization of olefins.
Finally, the document WO-A-095/35323 recommends the impregnation of an inorganic support, such as and preferably silica, in this order, by means of an alkylaluminium chloride (chlorinating agent and internal cocatalyst), then by means of a magnesium compound and finally by means of a titanium compound comprising chlorine. This specific procedure is supposed to result in a catalytic solid with an activity independent of the amount of transfer agent employed in the polymerization.
It has now been found that solid catalytic compositions of Ziegler-Natta type deposited on silica do not exhibit an optimum response to hydrogen.
The object of the present invention is to provide catalysts exhibiting a particularly high response to hydrogen which can be used in the polymerization of olefins.
To this end, the invention relates to a catalyst intended for the polymerization of olefins comprising a solid catalytic composition, based on a transition metal, on magnesium and on halogen, deposited on an inorganic support, characterized in that the inorganic support comprises aluminium phosphate (A) and at least one inorganic oxide (B) chosen from silica and alumina.
The invention is based on the surprising observation that recourse to a support comprising aluminium phosphate and an inorganic oxide chosen from silica and alumina results in catalysts with a response to hydrogen markedly greater than that of a similar catalyst in which the support is silica alone.
The content in the support of each of its constituents can vary within a fairly wide range. According to an advantageous alternative form of the invention, the support comprises aluminium phosphate (A) and an inorganic oxide (B) chosen from silica and alumina in an (A):(B) molar percentage of (90 to 5):(10 to 95). The support preferably comprises aluminium phosphate (X), silica (Y) and alumina (Z) and more particularly still aluminium phosphate (X), silica (Y) and alumina (Z) in a molar percentage of (1 to 85):(10 to 95):(1 to 80).
Supports of this type and processes for manufacturing them are known and disclosed in Patent BE-A-1,007,148 on behalf of Solvay Polyolefins Europe—Belgium.
The supports employed in the invention generally exhibit a specific surface of 100 to 800 m
2
/g, measured according to the volumetric BET method of British Standard 4359/1 (1984). The specific surface generally does not exceed 500 m
2
/g. It is preferably from 150 to 400 m
2
/g. Their crystallization temperature is preferably greater than 700° C. This temperature is determined by subjecting a sample of support to a heat treatment at different temperatures (500° C., 700° C., 800° C., 950° C, 1050° C.) and by subsequently examining this sample, after each heat treatment, by X-ray diffraction. The supports according to the invention generally exhibit a pore volume of approximately 0.5 to 4 cm
3
/g. The pore volume is the sum of the pore volume composed of pores with a radius of less than or equal to 75 Å, measured according to the nitrogen penetration (BET) method according to the volumetric technique described in British Standard BS 4359/1 (1984), and of the pore volume measured by the mercury penetration method, by means of a porosimeter of Poro 2000 type sold by Carlo Erba Co., according to Belgian Standard B 05-202 (1976). The supports according to the invention preferably exhibit a pore volume of approximately 1 to 3 cm
3
/g.
The support employed in the invention usually exhibits an apparent specific gravity of greater than or equal to 50 kg/m
3
, in particular of greater than or equal to 100 kg/m
3
; it is generally at most equal to 500 kg/m
3
, typically to 300 kg/m
3
. The apparent specific gravity is measured by free flow according to the following procedure: the powder of the support to be analysed is poured into a cylindrical receptacle with a capacity of 50 cm
3
, the powder being left loose, from a hopper, the lower edge of which is positioned 20 mm above the upper edge of the receptacle. The receptacle, filled with the powder, is subsequently weighed, the tare is deducted from the weight found and the result obtained (expressed in g) is divided by 50.
The supports employed in the invention are generally provided in the powder form, the grains of the powder having a diameter of 10 to 250 &mgr;m, generally of 25 to 150 &mgr;m. It is advantageous to subject them to a heat treatment before proceeding to the deposition of the catalytic composition. This heat treatment is generally carried out at a temperature at least equal to 150° C. and which, furthermore, does not exceed 1000° C. The heat treatment is generally carried out at a temperature at least equal to 250° C. and which does not exceed 875° C. The duration of the heat treatment usually amounts to 2 hours at least and generally does not exceed 18 hours.
The catalyst according to the invention (composed of the solid catalytic composition and of the inorganic support) generally comprises, per kg, at least 2 g of transition metal. The content of transition metal in the catalys
Detrez Charles
Koch Benoit
Bell Mark L.
Pasterczyk J.
Schneller Marina V.
Solvay Polyolefins Europe--Belgium (Societe Anonyme)
Venable
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