Process for polymerizing ethylene in a multi-stage polymerization process

A process of conducting polymerization of an ethylene homo- or copolymer comprising utilizing supported polymerization catalyst particles having a median particle size d50cat of from 5 to 30 μm in a multi-stage polymerization process in which at least two polymerization stages are connected in series and the last polymerization stage is conducted in a gas phase reactor, wherein

• (a) in a first polymerization stage, which is not a pre-polymerization stage, the catalyst activity is at least 15 kg/gcatalyst/h;
• (b) in each polymerization stage subsequent to said first polymerization stage, the catalyst activity is not more than 75% of the catalyst activity in said first polymerization stage;
• and
• (c) the particle size distribution of the supported polymerization catalyst particles (PSDcat) has a relative span following the inequation (II)
• spancat≤2.4−0.16·d50cat+0.0107·d50cat2−2.58·10−4·d50cat3 (II),
• wherein:
• spancat is the relative span of the particle size distribution of the supported polymerization catalyst particles (PSDcat) and is defined by the formula spancat=(d90cat−d10cat)/d50cat;
• d50cat is the diameter of the supported polymerization catalyst at which 50% of a sample's mass is comprised of particles with a diameter less than this value (median particle size) in μm;
• d90cat is the diameter of the particles of the supported polymerization catalyst at which 90% of the sample's mass is comprised of particles with a diameter less than this value in μm, and
• d10cat is the diameter of the particles of the supported polymerization catalyst at which 10% of the sample's mass is comprised of particles with a diameter less than this value in μm.

A process of conducting polymerization of an ethylene homo- or copolymer comprising utilizing supported polymerization catalyst particles having a median particle size d50cat of from 5 to 30 μm in a multi-stage polymerization process in which at least two polymerization stages are connected in series and a last polymerization stage is conducted in a double cone reactor wherein

• (a) in a first polymerization stage, which is not a pre-polymerization stage, the catalyst activity is at least 15 kg/gcatalyst/h;
• (b) in each polymerization stage subsequent to said first polymerization stage, the catalyst activity is not more than 75% of the catalyst activity in said first polymerization stage;
• and
• (c) the particle size distribution of the supported polymerization catalyst particles (PSDcat) has a relative span following the inequation (II)
• spancat≤2.81−0.20·d50cat+0.0131·d50cat2−3.12·10−4·d50cat3 (III)
• wherein:
• spancat is a relative span of the particle size distribution of the supported polymerization catalyst particles (PSDcat) and is defined by the formula spancat=(d90cat−d10cat)/d50cat;
• d50cat is the diameter of the particles of the supported polymerization catalyst at which 50% of a sample's mass is comprised of particles with a diameter less than this value (median particle size) in μm;
• d90cat is the diameter of the particles of the supported polymerization catalyst at which 90% of the sample's mass is comprised of particles with a diameter less than this value in μm, and
• d10cat is the diameter of the particles of the supported polymerization catalyst at which 10% of the sample's mass is comprised of particles with a diameter less than this value in μm.