Theoretical and experimental study of the interaction of methylaluminoxane (MAO)-low temperature treated silica: Role of trimethylaluminium (TMA)

摘要

This work presents an experimental and theoretical study of MAO-silica interaction. Several adsorption farms and proposed final species of MAO on silica support are considered. The reaction of silica-methylaluminoxane is thought to occur with OH from the surface, with CH4 evolution due to the reaction of the CH3 groups of MAO. Two forms of MAO are considered: linear and non-linear, taking account of the latest experimental evidence regarding MAO structures. It is known that nonextractable TMA remains from the preparation step in MAO. Therefore, TMA is considered in the modelling. The CH4 evolution was evaluated with chromatographic techniques during the preparation step of the support MAO-pre-treated silica. Silica was pre-treated at 300 degrees degrees C before use. The conclusion of this work is that OH from a silica surface reacts with MAO and probably with TMA during the MAO treatment. The most probable final species is one where the MAO molecule is fixed to the surface by several points, mainly in a linear form. TMA would be associated to MAO on the surface when MAO*TMA is supported. The reaction of TMA with the surface would be possible when MAO*TMA is supported. References: 29