Bp Chemicals Limited

University of Nottingham

John G Speakman

Jean-Claude A Bailly

Paul L Eve

Nicholas P Wilkinson

The present invention relates to a process for the polymerization of ethylene or copolymerization of ethylene and at least one other alpha-olefin, in the gas phase in a fluidized bed reactor, in the presence of a catalyst comprising chromium compounds associated with a granular support comprising a refractory oxide and activated by thermal treatment, which process is characterized in that the catalyst is used in the form of active particles of prepolymer, obtained by bringing the said catalyst in contact with ethylene, alone, or in a mixture with at least one higher alpha-olefin, in such a way that the prepolymer contains from 4.times.10.sup.-5 to 3 milligram atoms of chromium in the catalyst per gram.

Prepolymers of olefins containing a chromiumoxide and a granular

The present invention relates to a process for the polymerisation of ethylene or copolymerisation of ethylene and at least one other alpha-olefin, in the gas phase in a fluidised bed reactor, in the presence of a catalyst comprising chromium compounds associated with a granular support comprising a refractory oxide and activated by thermal treatment, which process is characterised in that the catalyst is used in the form of active particles of prepolymer, obtained by bringing the said catalyst in contact with ethylene, alone, or in a mixture with at least one higher alpha-olefin, in such a way that the prepolymer contains from 4.times.10.sup.-5 to 3 milligram atoms of chromium in the catalyst per gram.

Process for the polymerisation of ethylene or the copolymerisation of

A process and catalyst for polymerizing olefins, especially ethylene or a mixture of ethylene with up to 40 wt % (based on total monomer) or other 1-olefinic monomer, the process comprising (a) supporting a chromium compound on a refractory oxide support material, (b) adding one or more tetravalent titanium compounds, (c) heating the product under such conditions that an active polymerization catalyst in the presence of one or more organometallic compounds wherein the metal is of groups 1A, 2A, 2B or 3A of the Periodic Table (Mendeleef), especially aluminium trialkyls. Step (d) is preferably carried out in the presence of a polyene modifier. The refractory oxide support material is preferably silica. The produced polyolefins are also claimed.

Polymerization process

A supported Ziegler catalyst prepared by reacting, under substantially anhydrous conditions, a refractory oxide support material having acidic surface hydroxyl groups, e.g. silica, and an organo metallic compound, e.g. a trialkyl aluminium compound, separating any unreacted organo metallic compound and impregnating the solid product with a halogen-containing titanium compound and a halogen-containing vanadium compound. The catalyst, preferably together with a conventional Ziegler catalyst activator, e.g. an aliminium alkyl, is employed to polymerize 1-olefins, for example ethylene.

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West Lothian, United Kingdom

John G Speakman