THEORETICAL INVESTIGATION OF NOVELSILSESQUIOXANE-SUPPORTED PHILLIPS TYPE CATALYST BY DENSITY FUNCTIONAL THEORY (DFT)METHOD

摘要

In spite of great commercial importance of the Phillips CrOv/SiO2 catalyst and long term research efforts, the precise physico-chemical nature of active sites and polymerization mechanisms still remains unclear. The difficulties for a clear mechanistic understanding of this catalyst mainly come from the complexity of the surface chemistry of amorphous silica gel support. In this work, novel silsesquioxane-supported Phillips Cr catalysts are utilized as realistic models of the industrial catalyst for theoretical investigation using density functional theory (DFT) method in order to elucidate the effects of surface chemistry of silica gel in terms of supporting of chromium compounds and fluorination of silica surface on the catalytic properties of Phillips catalyst. Both qualitative and quantitative aspects with respect to various electronic properties and thermodynamic characteristics of the model catalysts were achieved. The future perspective of a state-of-the-art catalyst-design and mechanistic approaches for the heterogeneous SiO2-supported Phillips catalyst has been demonstrated.