INFRARED CHARACTERIZATION OF MGCL2 SUPPORTED ZIEGLER-NATTA CATALYSTS WITH MONOESTER AND DIESTER AS A MODIFIER

An i.r. study of MgCl2 supported TiCl4 Ziegler-Natta catalysts for pro pylene polymerization using Lewis base modifiers has been carried out. Two series of catalysts were prepared, differing mainly by the method used to prepare the MgCl2 support. One was prepared by precipitation and the other by ball-milling. Four different Lewis bases, of which tw o are diesters (di-2-ethyl phthalate and diisobutyl phthalate) and two are monoesters (ethyl benzoate and 2-ethyl hexyl benzoate), were empl oyed. The i.r. investigation of the catalyst was focused on the identi fication of complexes formed. It was found that the diester-containing catalysts contain significant amounts of TiCl4 . diester complexes an d phthaloyl mono- and di-chlorides complexed to MgCl2, whereas the mon oester-containing catalysts are virtually free of these compounds. The chlorides are believed to be formed from the reaction of TiCl4 and di ester weakly bonded to MgCl2. The TiCl4 . monoester complex is relativ ely weak so that the coordination of monoester with MgCl2 is much more favorable. The effects of the complexes, particularly their relative amounts, on the catalyst activity was investigated by carrying out pro pylene polymerizations with catalysts prepared by precipitation and by ball-milling method at three different activation temperatures.