Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Patent
1995-09-25
1998-12-22
Wu, David W.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
502132, 502133, 502200, 502202, 502204, 502206, 502209, 502210, 502211, 502213, 502219, 502222, 502223, 526117, 526118, 526134, 526169, 5261691, 5261692, 526170, 526172, 526351, 526352, C08F 422
Patent
active
058519467
DESCRIPTION:
BRIEF SUMMARY
The invention relates to coordination catalyst systems which comprise intramolecularly stabilized organometallic compounds. The usual coordination catalyst systems, which are usually based on transition metal compounds of sub-group IV to VIII and organometallic compounds of main group III of the Periodic Table of the Elements, are exceptionally diverse catalysts which are employed in chemical reactions of and with olefinically unsaturated compounds. These are, in particular, processes for the preparation of olefin polymers by coordination polymerization and metathesis of alkenes or alkynes. The preparation of polyethylene of increased density (high density polyethylene, HDPE) and of polymers and copolymers of ethylene, propylene or other 1-alkenes and alkynes is of considerable industrial importance. By catalysed metathesis, higher unsaturated hydrocarbon compounds can be prepared in a controlled manner from asymmetric alkenes and alkynes, and, from unsaturated cyclic hydrocarbon compounds, long-chain unsaturated hydrocarbons are obtained. The latter are used, for example, for the preparation of elastomers. Coordination catalysts, moreover, are used in other reactions, such as, for example, in alkene hydrogenation or in organometallic syntheses.
According to the current scientific knowledge on the action mechanism of coordination catalysts, it is assumed that a transition metal compound in each case forms the catalytically active center to which the olefinically unsaturated compound bonds by coordination in a first step. Olefin polymerization takes place via coordination of the monomers and a subsequent insertion reaction into a transition metal-carbon or a transition metal-hydrogen bond. The presence of organometallic compounds in the coordination catalyst systems or during the catalysed reaction is necessary in order to activate the catalyst, or maintain its activity, by reduction and, where appropriate, alkylation or formation of a complex system. These compounds are therefore also called cocatalysts. The compound containing the catalytically active transition metal atom is called the primary catalyst or precatalyst.
The best known industrially used catalyst systems for coordination polymerization are those of the "Ziegler-Natta catalyst" type and the "Phillips catalyst" type. The former comprise the reaction product of a metal alkyl or hydride of elements of the first three main groups of the Periodic Table and a reducible compound of a transition metal element of sub-group IV to VII, the combination used most frequently comprising an aluminium alkyl, such as diethylaluminium chloride, and titanium(IV) chloride. More recent highly active Ziegler-Natta catalysts are systems in which the titanium compound is fixed chemically to the surface of magnesium compounds, such as, in particular, magnesium chloride.
Chromium compounds bonded to inorganic supports are employed as a Phillips catalyst and undergo reduction or activation chiefly by organometallic compounds. Cr(II) is regarded as the catalytically active species ("reduced Phillips catalyst"). Here too, cocatalysts which are employed are chiefly aluminium alkyl compounds and alumoxane compounds.
More recent developments to give particularly efficient polymerization catalysts are directed towards metallocene compounds. Zirconocene compounds, for example, which are cyclopentadienyl complexes of zirconium alkyls or halides and derivatives thereof which are activated with the aid of aluminium, boron or phosphorus trialkyls or alumoxane, are known by the name "Kaminsky catalysts".
Use of these catalysts and related types in practice in the wide diversity of process variants developed can give products with sometimes extremely different properties. In the case of olefin polymers, which are generally known to be important as materials, the usability and use range depend, as a result of the properties, on the one hand on the nature of the monomers on which they are based and on the choice and ratio of comonomers and the typical physical parameters which charact
REFERENCES:
patent: 3154528 (1964-10-01), Kottenhahn
Hirsch Hans-Ludwig
Poetsch Eike
Pohl Ludwig
Schumann Herbert
Weiss Karin
Merck Patent Gesellschaft mit beschrankter Haftung
Wu David W.
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