Effect of Boron-modified MCM-41-supported dMMAO/Zirconocene Catalyst on Copolymerization of Ethylene/l-Octene for LLDPE Synthesis.

In this work, the boron (B) modification of MCM-41-supported dMMAO/zirconocene catalysts showed a promising increase (almost twice) in catalytic activity in ethylene/1-octene copolymerization. The enhanced activity can be attributed to the decreased interaction between the support and dMMAO with boron modification as was proved by TGA. It was proposed that boron acted as a spacer anchoring the support and dMMAO. However, at high boron loading (ca. 5 wt%), the activity slightly decreased due to the migration of dMMAO into boron layer resulting in less surface concentration of [AIJdMMAO which was measured by XPS. The inhibition of chain transfer reaction during polymerization apparently occurred upon the boron modification providing higher MW polymer. It was also suggested that boron modification has rendered more uniform catalytic sites which was leading to narrower MWD of the polymer observed. Based on 13CNMR, boron modification did not affect the microstructure of copolymers obtained. However, the insertion of 1-octene increased with boron modification probably due to decreased steric hindrance of the MCM-41 support.