Synthesis of mesoporous silica microspheres by a spray-assisted carbonation microreaction method

A novel spray-assisted carbonation microreaction method for the synthesis of mesoporous silica microspheres is reported. The synthetic process comprises the preparation of a silica sol via a carbonation reaction, rapid gelation at high temperature, and subsequent rapid solvent evaporation by spray drying. The carbonation microreaction was conducted in a membrane dispersion microreactor, in the presence of sodium silicate and carbon dioxide reactants. The as-synthesized silica microspheres exhibit a uniform mesostructure, excellent dispersity, and a narrow particle size distribution, with average diameters of 1–2 μm, Brunauer–Emmett–Teller surface areas of 300–1149 m2/g, and total pore volumes of 0.21–1.82 cm3/g. Relatively low concentrations of the silicate species and well-controlled silica condensation rates are responsible for the formation of the observed spherical morphology. The synthetic process is of significant practical importance as a result of using low-cost raw materials, and because of the excellent controllability and process stability displayed. Furthermore, this rapid and flexible method may be extended to the synthesis of various silica materials and their composites.