Copolymerization of ethylene/1-octene with boron-modified MCM-41-supported zirconocene catalyst

Abstract

In this research, effect of boron modification on the catalytic activity of the ethylene/1-octene copolymerization with rac-ethylenebis (indeny) zirconium dichloride [rac-Et(Ind) )[subscript 2]ZrCl[subscript 2]] catalyst system using MCM-41 with different pore sizes as support was studied. The properties of polymer produced were also investigated. The MCM-41 having small pore system with boron (B) modification gave higher activity than that of the MCM-41 having large pore at the same condition. This was attributed to the dispersion and interaction between [Al][subscript dMMAO] and supports as proven by EDX and TGA techniques. It was found that small pore system exhibited higher amounts of [Al][subscript dMMAO] than the large pore system. The highest activity was observed from MCM-41 with 1% wt of B modification. The molecular weight of polymer obtained from this supported system was higher than for the copolymer normally produced from the corresponding homogeneous system. For the small pore system, the inhibition of chain transfer reaction during polymerization apparently occurred upon the B modification indicating higher MW of polymer. On the contrary for the large pore system, it exhibited lower MW of polymer with B modification. For both the MCM-41 small pore and large pore (especially at low content of B) system, it was also suggested that B modification rendered more uniform catalytic sites leading to narrow MWD of polymer observed. There was no significant change in the polymer molecular structure by means of [superscript 13]C NMR. It can be also stated that the addition of B into MCM-41 support affected the insertion of 1-octene, T[subscript m] and crystallinity of polymer produced.