Synthesis of hollow silica spheres SBA-16 with large-pore diameter

Hollow silica SBA-16 spheres with cubic ordered mesoporous shells were synthesized by an emulsion-templating method, using Pluronic F127 as a structure-directing agent, tetraethyl orthosilicateas as a silica source and heptane as a cosolvent in the presence of NH₄F. The size of these spheres is in the range of 10 to 30 μm. The shell is about 700 nm thick and consists of large pores, ~ 9 nm in diameter, arranged in a cubic order. After calcination, the spheres maintain their mesoporosity and show a high surface area of 822 m²/g. The formation mechanism of the silica hollow spheres is discussed.