Characterization of phthalate internal donor in MgCl۲ supported Ziegler-Natta catalyst by solid state ۱۳C NMR

Ziegler-Natta catalyst for propylene polymerization, which TiCl۴ and di-alkyl phthalate were supported on MgCl۲, was analyzed by solid state ۱۳C NMR. It was confirmed that the spin-lattice relaxation time (“relaxation time” hereafter) of carbonyl group in phthalate was shortened with increasing measurement temperature as a general manner because of the enhancing of molecular mobility at high temperature. The degree of the relaxation period reduction with temperature was influenced by the alkyl group size in phthalate molecule; the larger alkyl group showed a greater shorting of the relaxation period. A short relaxation time should suggest a weak interaction between the phthalate molecule and the MgCl۲ support surface. The change in catalytic performance was discussed by the active site formation mechanism involving the phthalate removal step. 

Keywords:

Ziegler-Natta catalyst , propene polymerization , solid-state ۱۳C NMR , spin-lattice Relaxation time , carbonyl(C=O) motion in phthalate molecular