ONE-PHASE SUPPORTED TITANIUM-BASED CATALYSTS FOR POLYMERIZATION OF ETHYLENE .2. EFFECT OF HYDROGEN

The relation between composition of the one-phase titanium-based silic a supported catalysts for gas-phase ethylene polymerization, and the a bility of these catalysts to control the molecular weight of polymer u sing hydrogen has been studied. Halogen containing alkyl-aluminium com pounds and alkoxy groups on titanium promote the chain transfer proces s. A significant polymerization rate lowering effect is caused by hydr ogen. However, catalyst activity fully revives after hydrogen removal from the polymerization system. The proportion of active titanium was found to be 18+/-4% in the presence of hydrogen, and the value of prop agation rate constant k(p) was calculated to be 190+/-45 L/mol.s.