Highly steam-stable mesoporous silica assembled from preformed zeolite precursors at high temperatures

Abstract

Mesoporous silica (JLU-20-S) is successfully synthesized at high-temperatures (180–220 °C) by the assembly of preformed silicalite-I zeolite nanoclusters with a mixture of triblock copolymer surfactant (P123) and fluorocarbon surfactant (FC-4). The preformed silicalite-I nanoclusters are obtained by heating, at 100–120 °C for 2–3 h, silica gels at SiO₂/(TPA)₂O/H₂O molar ratios of 1/0.14/36. Mesoporous JLU-20-S shows extraordinary stability in steam (800 °C, 4 hours), compared with other mesoporous silica materials (JLU-20 synthesized at 190 °C, MPS-9 prepared from preformed silicalite-I zeolite nanoclusters at 100 °C, and SBA-15). The results of X-ray diffraction and transmission electron microscopy show that JLU-20-S has a hexagonal mesoporous symmetry, and the data obtained from N₂ isotherms show that JLU-20-S contains both mesopores and micropores. The high steaming stability of the mesoporous silica of JLU-20-S is possibly related to synergistic advantages of both high-temperature synthesis and preformed zeolite nanoclusters in the synthesis of ordered mesoporous silica materials, and the observed microporous volume in JLU-20-S is attributed to the use of preformed zeolite nanoclusters.