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
1997-11-03
2003-04-08
Lu, Caixia (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S111000, C502S115000, C502S116000, C502S125000, C502S126000, C502S127000, C502S132000, C526S124500, C526S124600
Reexamination Certificate
active
06544920
ABSTRACT:
This application is a U.S. National Stage of International application PCT/EP96/05659, filed Dec. 17, 1996, and published on Jul. 3, 1997 in the English Language.
The present invention concerns solid catalyst components comprising magnesium chloride and a titanium compound supported on metal oxides, and catalysts obtained from them.
Said components and catalysts find a particular application in the polymerization of CH
2
═CHR &agr;-olefins where R is hydrogen or an alkyl radical with 1-6 carbon atoms, or an aryl radical, in particular a phenyl radical.
In the art are known and described many examples of solid components and catalysts of the above mentioned type obtained by way of various preparation methods.
The interest in developing catalysts where the magnesium chloride and the titanium are supported on metal oxides is due to the many advantages that said catalysts offer, such as:
reduction in the content of halogens in the polymer obtained with said catalysts, due to their reduced content of halogens compared to the catalysts comprising a component supported on magnesium chloride;
simplicity in the preparation;
the availability in the market of metal oxides adequate for the preparation of the catalysts.
Obviously said reduction in the content of halogens is greater as the yield of the polymerization of the catalyst increases.
However, the catalysts comprising a component supported on magnesium chloride, and therefore not containing metal oxides, allow one to obtain polymers having higher bulk density compared to the catalysts having the magnesium chloride and the titanium compound supported on metal oxides.
For example, published European patent application n. 506074 describes catalysts supported on metal oxides that allow one to obtain high yields in the polymerization of olefins, however the examples show that the polymer obtained has a tamped bulk density which does not exceed 0.46 g/cm
3
.
Therefore, it would be particularly desirable to obtain a catalyst supported on metal oxides that would be capable of producing, with high yields, polymers having a higher bulk density.
In fact, a higher bulk density facilitates the conveying and processing of the polymers, and allows the polymerization plants to maintain high levels of productivity, particularly in liquid polymer.
SUMMARY OF THE INVENTION
As an answer to this need, the Petitioner realized a solid catalyst component for the polymerization of olefins, which constitutes one object of the present invention, comprising the product of the direct reaction, with no subsequent reactions with reducing organometallic compounds, between a titanium compound containing at least one Ti-halogen bond, optionally an electron-donor compound, and a support obtained by contacting a metal oxide containing hydroxyl groups with a solution comprising:
A) magnesium chloride;
B) an alcohol in quantities ranging from 1 to 6 moles, preferably from 2 to 4 moles, per mole of magnesium chloride,
in an organic solvent capable of bringing the magnesium chloride in solution in quantities greater than or equal to 5 g per liter, preferably greater than or equal to 10 g per liter in the presence of the above mentioned quantities of alcohol B), said solvent, however, not being able to form adducts with the magnesium chloride.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The catalysts obtained from the above mentioned solid component are capable of producing polyolefins in free-flowing particles having a tamped bulk density even higher than 0.5 g/cm
3
.
Moreover, said polyolefins contain a particularly small fraction of fine particles (i.e., having a diameter smaller than or equal to 500 &mgr;m), generally less that 1% by weight, while the micro-fines (i.e., polymer particles with a diameter smaller than 106 &mgr;m) are substantially absent. Said characteristic constitutes a further advantage, because low contents of fine particles contribute to facilitate the conveying and processing of the polymers. In addition, the absence of micro-fines contributes to the elimination of fouling and plugging phenomena in the polymerization plants and in the polymer conveyance plants.
A further advantage of the catalyst components of the present invention is the extreme simplicity of the process used for their preparation.
In fact there is no need for any physical or chemical treatment of the metal oxide before it is contacted with the solution of magnesium chloride and alcohol B) in solvent C). Moreover the reaction with the titanium compound containing at least one Ti-halogen bond is carried out by adding said titanium compound to the suspension of metal oxide in the solvent C), resulting from the contact with the above mentioned solution, or after removing the solvent C) from the suspension, preferably by evaporation. The reaction with the electron-donor compound, when used, may occur before, during or after the reaction with the titanium compound. The reactions with the titanium compound and the electron-donor compound, therefore, occur directly, without treatments or intermediate reactions after the contact between the metal oxide and the solution of A)and B) in C), other than the removal of C) and partial removal of B) (both being optional), and without further reactions with reducing organometallic compounds.
Said preparation process is particularly simplified compared to the process described in published European patent application n. 408 750, which requires the use of solutions of magnesium chloride and alcohols in organic solvents, but needs to carry out the following steps:
treatment of the metal oxide, before the contact with the above mentioned solutions, with an organometallic compound of the groups from II to IIIA of the periodic table, or with a halogenated compound;
treatment of the product of the contact with the above mentioned solutions, either before, during or after the reaction with a titanium compound, with a reducing organometallic compound.
In addition, in all of the examples of the above mentioned European patent application, the metal oxide is previously subjected to heat treatments. The same examples show that in spite of the complexity of the catalyst preparation process, the polymer obtained from it has relatively low bulk density values. Moreover, the above mentioned catalyst is suitable only for the polymerization and copolymerization of ethylene, while the catalyst of the present invention is capable of producing highly isotactic polypropylene with all the advantages described above.
Particularly preferred among the metal oxides that can be used in the preparation of the solid catalyst component of the present invention are the silica, alumina, the mixed Al and Si oxides, magnesium oxide, and titanium dioxide.
As already stated, the metal oxides are not subjected to physical or chemical treatments before being contacted with the magnesium chloride solution, therefore they contain hydroxyl groups in quantities generally ranging from 1 to 3 mmoles per gram.
Preferably they contain also free water, i.e., water that is not chemically bonded but is only absorbed into the metal oxide, in quantities generally up to 15 mmoles per gram, in particular ranging from 0.1 to 15 mmoles per gram. The determination of the quantity of hydroxyls can be made according to the method described in J. Phys. Chem. 66 800 (1962), and that of the free water by way of the Fisher reagent.
Preferably the metal oxides have a pore volume (B.E.T.) greater than 0.3 cm
3
/g, and generally ranging from 0.5 to 3.5 cm
3
/g, while the surface area (B.E.T.) of said oxides can vary within rather wide limits, for example from 30 to 1000 m
2
/g, preferably from 200 to 500 m
2
/g.
Examples of solvents C) are aromatic hydrocarbons, and aliphatic, cycloaliphatic, or aromatic halogenated hydrocarbons. The preferred ones are the halogenated hydrocarbons, in particular the aliphatic or cycloaliphatic chlorinated or brominated hydrocarbons, either saturated or unsaturated, or aromatic hydrocarbons, containing 5-20, more preferably 6-12 carbon atoms.
Specific examples of aro
Arletti Arrigo
Morini Giampiero
Pennini Gianni
Basell Poliolefine Italia S.p.A.
Lu Caixia
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