Single-site catalysts for ethylene polymerization, their preparation and uses

摘要

PURPOSE: A single-site catalyst for preparing polyethylene, its preparation method and a polymerization method of polyethylene using the catalyst are provided, to obtain polyethylene which has the larger molecular weight and the narrower distribution of molecular weight. CONSTITUTION: The single-site catalyst is represented by the formula 1, 2 or 3, and has a ligand capable of covalent binding or coordinating binding with a central metal simultaneously, wherein M is a metal of the group 3 in the periodic table, a transition metal of the group 4-10 in the periodic table or a metal of the lanthanide series; A is a bridging group selected from an alkyl group of C1-C20, an aryl group, a silyl group or a halogenated alkyl group; B is N, P or an element of the group 5B in the periodic table; C is a 5-7 membered ring ligand having a substituent selected from a halogen, an alkyl, an aryl, a silyl, an alkoxy, a haloalkyl, or a haloallyl group containing 1-20 elements except H; D is O, S or en element of the group 6B in the periodic table; and L is an anion or a Lewis base having a substituent selected from a halogen, an alkyl, an aryl, a silyl, an amine, an amide, an allyloxy, an alkoxy, a haloalkyl, or a haloallyl group containing 1-20 elements except H. Preferably M is Ti, Zr or Hf.