Effect of Ga modification on different pore size silicas in synthesis of LLDPE by copolymerization of ethylene and 1-hexene with [t-BuNSiMe2Flu]TiMe2/MMAO catalyst

摘要

Copolymerization of ethylene and 1-hexene for obtaining the linear low-density polyethylene was conducted along with silicas as supports for [t-BuNSiMe2Flu]TiMe2/MMAO catalyst. Two silicas with different pore sizes were used to investigate the effect of pore sizes on copolymerization. In addition, gallium was also introduced into both silicas to improve their properties and enhance the catalytic activities of the system. It was found that before modification, the larger pore silica exhibited higher catalytic activity than the smaller one due to low internal diffusion resistance. After modification, both silicas exhibited higher catalytic activity comparing to their pristine condition. However, 1-hexene incorporation in the obtained copolymers was lower. The reduced surface area of silica after modification was the main reason for the decrease in 1-hexene incorporation. The properties of the copolymers by means of differential scanning calorimetry, gel permeation chromatography, and 13C NMR spectroscopy were further discussed in more detail.