Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Patent
1993-08-16
1996-01-02
Cross, E. Rollins
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
502103, 502110, 502114, 5261231, 526129, B01J 3112, C08F 442, C08F 200
Patent
active
054808499
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the preparation of a solid procatalyst composition of a catalyst system for the polymerization of olefins wherein a carrier is impregnated with a magnesium halide dissolved or suspended in a monocarboxylic acid alkyl ester, and the impregnated carrier is reacted with an organometallic compound or a silicon compound and treated with a transition metal compound.
In the polymerization of olefins a so called Ziegler-Natta-catalyst system consisting of a so called procatalyst and a co-catalyst usually is used. The procatalyst is based on a compound of a transition metal belonging to some of the groups IVB-VIII of the periodic system of the elements and the co-catalyst is based on an organometallic compound of a metal belonging to some of the groups IA-IIIA of the periodic system of the elements.
It is conventional to use in the preparation of heterogeneous polymerization catalysts as a component enhancing the polymerization activity of the procatalysts a support carrier on which the transition metal compound is superposed. Usual carriers are silica, aluminum oxide, magnesium oxide, titanium oxide, carbon in different forms an different polymer types. Important carriers include the magnesium compounds such as alkoxides, hydroxides, hydroxy halides and halides, of which the latter, in particular magnesium dichloride, have recently become the most significant carrier components of procatalyst compositions.
Because magnesium halides are in their base crystal form not activated very efficiently with a transition metal compound, their crystal form has to be deformed. Traditionally this is carried out by grinding e.g. in a ball mill typically resulting in a finely divided powder with a large specific surface the particles of which have a strongly deformed crystal lattices. When such a powder is activated to a procatalyst composition by superposing on it a transition metal compound, and thereafter reduced with an organometallic compound as a co-catalyst, a very active polymerization catalyst is obtained.
The usual method for grinding magnesium halide include the drawbacks that it is very energy consuming, causes wearing and corrosion of the apparatus and is suited to the production of catalyst only with the tedious batch process.
A more modern method to lessen the crystallinity of the magnesium halide and thereby enhance its ability to become activated with a transition metal compound is to modify it chemically. Thereby a magnesium halide, an electron donor and a transition metal compound are reacted with each other, often in a solution, to an easily isolated procatalyst composition.
U.S. Pat. Nos. 4,124,532 and 4,174,429 describe the preparation of this kind of catalytically active complex by reacting a magnesium halide and a transition metal compound at a suitable ratio in a electron donor solvent. The finished complex can be separated through crystallization, by evaporation of the said solvent, or by mixing the complex with a solvent in which is not soluble. Because such complex compounds are formed as a result of a spontaneous crystallization, their crystal structure is very regular and activity correspondingly rather limited.
U.S. Pat. No. 4,302,566 and EP Patent Application 6,110 describe a precursor formed by a magnesium halide, a transition metal compound and an electron donor. The precursor is formed by precipitation from an electron donor solution whereafter it is separated and mixed with an aluminumalkyl and a separate inert carrier.
In these processes an essentially amorphous procatalyst composition is not formed either, because the precursor in question is crystallized in the preparation spontaneously and its morphology is not essentially changed after that.
Other patent publications describe Ziegler-Natta procatalysts on a silica or magnesium silicate carrier but do not take advantage of the superior ability of the magnesium compounds to activate transition metals. Such publications include e.g.: WO-88/02376, EP-215,916, EP-120,503, EP-91,135, EP-80,052, EP-55
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Gustafsson Bill
Kostiainen Arja
Sormunen Pekka
Borealis Holding A/S
Cross E. Rollins
Griffin Walter D.
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