Rapid Synthesis of Al-Containing Mesoporous Silica Hard Spheres of 30−50 μm Diameter

Al-containing mesoporous silica hard spheres of 30−50 μm mean diameter have first been synthesized at room temperature in 80 min using 1-alkylamine as a structure-directing agent. The formation of the spheres occurs only within a definite range of molar synthesis compositions of Si, Al, HCl, H2O, and 1-alkylamine, especially HCl molar concentration. Scanning electron microscopic observation and particle size analysis revealed that the spherical products obtained by octylamine templating resulted in a higher uniformity in particle size, and the addition of ethanol into the reaction mixture afforded even more uniform particle size distribution. Textural mesoporosity along with framework mesoporosity for the spheres was observed with octylamine templating, while no textural porosity was found for the spheres produced by other amines. The calcined spheres with a pore structure lacking long-range order have BET surface areas of over 800 m2/g at 600 °C. The Al-containing silica spheres have medium-strength acid sites which are weaker than those usually present in zeolites.