27Al NMR MAS Study of the Surface Al Complexes Formed in Reaction of Organoaluminium Compounds with Supported TiCl4/MgCl2 Catalyst
Journal of Molecular Catalysis A: Chemical
||27Al NMR MAS, Olefin polymerization, Supported Ziegler-Natta catalysts
Boreskov Institute of Catalysis SB RAS
Full-size image (<1 K) NMR MAS method has been used to study the surface aluminium compounds forming during the treatment of supported TiCl4/MgCl2 catalyst with organoaluminium compounds (OAC) of various composition (AlEt3, AlOct3, AlEt2Cl). Dialkylaluminium chloride has been found to be the main surface compound in the case of trialkylaliminium. Three surface species of dialkylaluminium chloride have been identified: one of them corresponds to 5-coordinated aluminium; the other two correspond to 6-coordinated aluminium with different alkyl-to-chlorine ratio. The relative amounts of surface species depend on the conditions of OAC reaction with catalysts and OAC composition. After polymerization of ethylene or propylene on trioctylaluminium-treated catalysts (polymer yield ca. 1 g/1 g catalyst), the signals of 5-coordinated aluminium disappear from the Full-size image (<1 K) NMR spectra of the catalysts.