Gas-phase ethylene polymerization with the polyphenoxide ligand tris(2,6-dihydroxyphenyl)ethene: Development of a new silica-supported titanium-magnesium catalyst

Silica-supported polymerization catalysts were prepared with the polyphenoxide ligand 1,1,2-tris(2,6-dihydroxyphenyl)ethene. The effect of catalyst preparation conditions on gas-phase activity profiles for ethylene homopolymerization and ethylene/1-hexene copolymerization were studied. Reactor conditions such as co-catalyst concentration, temperature, pressure, hydrogen concentration, and comonomer concentration were varied to examine the effect on activity and polymer properties. The bimetallic (Ti-Mg) polyphenoxide catalyst had significantly higher polymerization activities than catalysts prepared without the ligand.;Catalyst and polymer characteristics were examined with various techniques. Particle size distributions and surface areas were measured, and elemental analysis was performed for titanium and magnesium contents. Molar masses were measured with size exclusion chromatography (SEC), and temperature rising elution fractionation (TREF) was used to assess comonomer incorporation. Surface and internal structures of polymer particles were explored with scanning electron microscopy (SEM). Characterization studies showed the Ti-Mg polyphenoxide catalyst had low 1-hexene incorporation and that molar masses can be controlled with hydrogen.