Control of the Porosity and Morphology of Ordered Mesoporous Silica by Varying Calcination Conditions

Abstract

Abstract In this study, mesoporous silica (SBA-15) was prepared using pluronic P123 surfactant as the structure-directing template, HCl as catalyst and tetraethyl orthosilicate as the silica source. SBA-15 prepared were then dried at 110 o C and calcined at different temperatures (200-700 °C) and were characterized in detail by Fourier transform infrared spectrophotometer (FTIR), scanning electron microscope (SEM), thermogravimetric analysis (TGA) and BET surface analyzer. FTIR analysis shows that silica calcined at 110 and 200 o C show characteristic bands for the surfactant which diminishes at 300 o C; indicating incomplete removal of the surfactant. TGA analysis of as-synthesized, uncalcined SBA-15 shows that the degradation of the surfactant is completed at 300 o C. The surface area, total pore volume and mean pore radius increase with increasing calcination temperature up to 500 o C and then decrease at 700 o C. Silica dried at 110 o C and calcined at 200 o C shows almost no porosity, while porous nature starts to appear when silica is calcined at 300 o C. The surface area, mean pore radius and total pore volume of mesoporous silica also show dependence on the calcination time, where the sample calcined for 10.5 h show the highest surface area and pore volume. The condition to obtain highest surface properties and porosity of SBA-15 has been optimized as calcination temperature of 500 o C for a period of 10.5 h.