Silsesquioxane‐Supported Chromium Catalyst for Insight into Phillips‐Type Ethylene Polymerization

Abstract To investigate the Phillips catalyst for ethylene polymerization, a family of silsesquioxane‐supported chromium catalysts with a bipodal structure have been synthesized from trivalent or hexavalent chromium precursor and fully characterized by 1 H/ 13 C/ 29 Si NMR, FT‐IR, and UV–vis spectroscopies. Upon activation with tri‐ n ‐octylaluminum or butylated hydroxytoluene (BHT) modified TIBA following the “TIBA‐BHT”, all the silsesquioxane‐supported chromium catalysts display moderate activities (50–523 g‐PE•g‐cat −1 ·h −1 ) for ethylene polymerization, producing polyethylene (PE) with high methyl branching level (0.1–1.3/1000C) and a clear bimodal molecular weight distribution (MWD). Catalysts with hexavalent chromium precursor exhibit higher activities than trivalent ones. The type of activator and coordination environments of the active site play a key role in the MWD of obtained PE.