Ethylene/1-Octene Copolymerization over Ga-modified SiO2-supported Zirconocene/MMAO Catalyst Using In Situ and Ex Situ Impregnation Methods

Ethylene/1-octene copolymerization over the SiO2-supported zirconocene/MMAO catalysts was investigated. The silica support was modified by different batches of 1.0 and 0.2 wt% Ga. It was found that Ga was well-dispersed all over the silica granules which cannot be detected by XRD. Based on the EDX measurement, it was revealed that Ga-modification increased the adsorption ability of MMAO on the silica support after impregnation. Thus, Ga-modification showed a promising way to enhance the rate of ethylene/1-octene copolymerization. Based on TGA study, lower interactions between MMAO and support caused by Ga-modification was another reason for increase in catalytic activity. Moreover, the Ga-modification increased Lewis acid centres or active species on the catalytic system. In addition, a comparative study of polymerization was also conducted with in situ and ex situ impregnation methods. It was found that the in situ impregnation method of the MMAO onto silica exhibited remarkable (almost 3 times) activity compared to ex situ method which is attributed to lower deactivation effect of the catalyst. 13C NMR analysis, however, indicated that only random copolymers were produced in all systems. These results could be related to the high degree of 1-octene insertion and thus amorphous copolymers were produced in all systems.