Superactive and stereospecific catalysts. IV. Influence of structure of esters on MgCl2 supported olefin polymerization catalysts

CH-type catalysts were prepared by reacting MgCl₂ · ROH, where ROH is 2-ethyl hexanol (EH), (R)-2-octanol (R-20), and (S)-2-octanol (S-20), with TiCl₄ in the presence of di-i-butyl phthalate (BP), di-i-butyl terephthalate (BT), (-)-dimenthyl phthalate (MP), or (-)-dimenthyl terephthalate (MT). The MT catalysts were found to incorporate 8.9 to 13% Ti whereas the BP catalysts contain only 1.9 to 2.6% Ti. Comparison of the CH(EH, BP) and CH(EH, MT) catalysts showed that they have about equal number of isospecific active sites per gram of catalyst and the same rate constants of propagation for their nonspecific sites, however, the isospecific sites in the latter are less active by comparison. Consequently, the CH(EH, BP) catalysts is five times more active than the CH(EH, MT) catalysts and produces polypropylene which is 97% isotactic (reflux n-heptane insoluble) as compared to 84.7% for the latter. The catalysts derived from 2-octanols are much less active than the corresponding catalysts prepared with 2-ethyl hexanol due to lack of reactivity with phthalic anhydride which permits excessive incorporation of TiCl₄ to form nonstereospecific catalytic sites as well as inactive Ti species.