Patent ID: 8841391
Filing Date: 2014-09-23
Classification: C08F

Abstract:
1. A process for the introduction of a metallocene polymerisation catalyst in solid form into a gas-phase fluidised bed reactor, which process comprises using an injection device having an inner tube of internal cross-sectional area of 10 to 100 mm 2 and an outer tube forming an annulus around said inner tube with a cross-sectional area of 2 to 10 times the internal cross-sectional area of the inner tube, and passing said polymerisation catalyst and a carrier gas through the inner tube and into the gas-phase fluidised bed at a linear velocity of said carrier gas of 4 to 20 m/s and at a mass flow rate of carrier gas in the range 10-35 kg/h, and passing a shielding gas through the outer tube and into the gas-phase fluidised bed reactor at a linear velocity of said shielding gas of 1 to 10 times the linear velocity of the carrier gas through the inner tube and at a mass flow rate of the shielding gas in the range 100-500 kg/h, wherein the shielding gas comprises ethylene and hydrogen in a molar ratio of hydrogen to ethylene which is higher than the molar ratio of hydrogen to ethylene at the gas outlet of the fluidised bed reactor.