Mesoporous SiO2 powders with high specific surface area by microwave drying of hydrogels: A facile synthesis

The conventional synthesis routes used for the production of mesoporous silica with high specific surface area (>500 m2/g) are often characterized by high production costs and tedious processing. The present work was therefore aimed to develop a cost-effective and rapid process for the production of mesoporous silica using a cheap source such as water-glass and microwave drying of the wet gels at an ambient pressure. The organic modification of the hydrogels in aqueous phase by trimethylsilyl (–Si–(CH3)3) groups was a crucial step during the processing which preserved mesopores (pore diameter, 2–50 nm) in the microwave dried silica. The unmodified hydrogel underwent tremendous shrinkage during the drying and yielded microporous silica. Using this novel route, mesoporous silica with specific surface area as high as 640 m2/g and the cumulative pore volume maximum up to 0.94 cc/g, could easily be synthesized in three hours. The silica powders exhibited tapping densities in the range of 0.60–0.87 g/cm3. The effect of microwave drying period on the textural properties such as specific surface area, pore size distribution and cumulative pore volume, has been investigated and discussed.