ONE-PHASE SUPPORTED TITANIUM-BASED CATALYST FOR POLYMERIZATION OF ETHYLENE .4. EFFECT OF ALKYL GROUP AT ORGANOALUMINUM COMPOUND ON CATALYSTPERFORMANCE

The effect of a basic layer (SiO2-R(3)Al intermediate) in the one-phas e silica supported titanium-based catalyst was investigated using the simple model catalyst systems obtained by reacting the activated silic a gel consecutively with R(3)Al and TiCl4. Mode of the interaction of SiO2 with R(3)Al-resulting in the formation of the basic layer-was obs erved via analysis of the concentration of the unreacted OH groups on the silica surface employing IR spectroscopy and via analysis of the c oncentration of aluminium in solvent using AA spectroscopy. It was fou nd that nature of the alkyl group in R(3)Al modified the structure of the basic layer, thus influencing the catalyst performance including t he concentration of both the sum of Ti2+ and Ti3+ and the ESR-active T i (III) centers. The sum of Ti2+ and Ti3+ ranged from 45 to 52 mol % a nd the amount of the ESR-active Ti (III) species ranged from 6 to 17 m ol % of the all titanium content. A significant effect of alkyl group at organoaluminium compound on the molecular weight distribution of th e resulting polymer was observed. (C) 1996 John Wiley & Sons, Inc.