SURFACE ACIDIC SITES ON SUPPORTED TITANIUM-MAGNESIUM CATALYST FOR PROPYLENE POLYMERIZATION - ESR STUDY VIA ADSORPTION OF STABLE NITROXYL RADICALS

ESR was used for studying the interaction between the stable nitroxyl radical TEMPO (2,2,6,6-tetramethylpyperidin-1-oxyl) and the titanium-m agnesium catalysts TiCl4/MgCl2 and TiCl4/MgCl2 . nD (D is either diiso butyl phthalate or 2,2-diisobutyl-1,3-dimethoxypropane), as well as Ti Cl4/MgCl2 . nD treated with triethylaluminium. In all cases, only part of the surface titanium complexes (18-53 mol-%) exhibit Lewis acid pr operties and can interact with TEMPO. The portion of titanium complexe s with acidic properties depends on the composition and preparation of the catalysts, and it decreases upon treatment with triethylaluminium .