Synthesis of mesoporous silica/polymer composites with controlled pore sizes and their application to esterification Rreaction

Abstract

The discovery of ordered mesoporous silica opened a synthesis route to new families of porous materials. Many studies have been investigated to control the synthesis conditions and prepare new mesostructured materials. There were tremendous interests towards the applications of the mesoprous silicas. A particularly interesting approach has been discovered recently for the synthesis of mesoporous silica/polymer composites. The objective of this thesis work was to synthesize such silica/polymer composite materials with controllable pore diameters and therefore to investigate the effect of pore diameter on the catalytic properties. The silica/polymer composite materials were synthesized, following the synthesis strategy reported before. Silica/polymer composites with tunable pore sizes were obtained through the incorporation of polystyrene into the 2D hexagonal mesoporous silica SBA-15 with different pore sizes. The pore size control was achieved through variation of surfactants and hydrothermal temperatures during the silica synthesis. The synthesis of mesoporous silica SBA-15 was carried out under the dilute acidic condition, in the light of facile thermodynamic control discovered recently. These mesoporous silicas SBA-15 served as an inorganic framework for the preparation of composite materials. The polymer moiety was then sulfonated with sulfuric acid. Catalytic properties of these acid-functionalized composite materials were studied for the esterification reaction of benzyl alcohol with hexanoic acid. The effects of the pore sizes on the catalytic activity and selectivity were investigated. The results showed that both activity and selectivity increased with the decrease of the pore size. Based on the promising results, we propose that the composite materials synthesized under present conditions and strategy would find applications for other catalytic reactions.