HEXENE-1 POLYMERIZATION BY HOMOGENEOUS ZIRCONOCENE AND HETEROGENEOUS-SUPPORTED TICL3 CATALYSTS

MgCl2-supported TiCl3 catalysts, with and/or without electron donor modifier (internal B(i) or external B(e)), were compared with rac-ethylenebis(indenyl)zirconium dichloride (1) activated with either MAO or the cation forming agent, triphenyl carbenium tetrakis (pentafluorophenyl) borate (2), with triethylalumium (TEA). The activities of the heterogeneous catalysts depend on the presence or absence of the Lewis base, were relatively insensitive to the temperature of polymerization, and produce poly (hexene) with molecular weights up to 10(6). The 1/MAO catalyst has about five times higher activity at 50-degrees-C but is almost inactive at -30-degrees-C; the overall activation energy is 12.4 kcal mol-1. In contrast, the activity for hexene polymerization by the 1/2/TEA catalyst is actually slightly greater at lower temperature. The MW's of poly (hexene) obtained with the zirconocenium catalysts are only in the tens of thousands because of rapid beta-hydride elimination by the electrophilic cationic Zr center.