Process for the gas phase polymerisation of olefins
AssigneeBP Chemicals Limited
InventorJean-Jacques Kuhlburger
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Abstract
The present invention relates to a process for preparing high density polyethylene in the gas phase comprising contacting ethylene or a mixture comprising ethylene and one or more alpha-olefins with a chromium oxide catalyst supported on a granular or microspherical refractory oxide in a fluidised bed reactor in the presence of oxigen. The present invention further relates to a process for controlling the density of high density polyethylene prepared in the gas phase comprising contacting ethylene or a mixture comprising ethylene and one or more alpha-olefins with a chromium oxide catalyst supported on a granular or microspherical refractory oxide in a fluidised bed reactor in the presence of oxigen.
Claims6
Process for preparing high density polyethylene in the gas phase comprising contacting ethylene or a mixture comprising ethylene and one or more alpha-olefins with a chromium oxide catalyst supported on a granular or microspherical refractory oxide in a fluidised bed reactor having a recycle gas line, under polymerisation conditions, characterised in that
- (i) oxygen is introduced into the reactor in the range of about 0.03 to about 1 part by volume of oxygen per million parts by volume of ethylene;
- (ii) an organoaluminium compound is introduced into the reactor in the range of 0.0001 to 0.05 mole per ton of ethylene;
- and
- (iii) the polymerisation is carried out at a temperature in the range of 80 to 120° C.
Process according to any of the preceding claims wherein the chromium oxide catalyst supported on a granular or microspherical refractory oxide is a titanium or aluminium modified silica supported chromium oxide catalyst.
Process according to any of the preceding claims wherein the organoaluminium compound is introduced into the reactor in the range of 0.001 to 0.01 mole per ton of ethylene.
Process according to any of the preceding claims wherein the organoaluminium compound is a trialkylaluminium, preferably triethylaluminium.
Dependencies are inferred from the claim text.