Time-Resolved in Situ X-ray Powder Diffraction Study of the Formation of Mesoporous Silicates

Abstract

In situ, time-resolved energy-dispersive X-ray diffraction has been used to investigate the formation of the mesoporous silicates FSM-16 and MCM-41. The data suggest that the silica−surfactant mesophases formed are highly dependent on the reactant medium, the effect of the silica source being one of the main determining factors. Kanemite, a layered polysilicate, proves to be an excellent silicate source, giving rise to relatively ordered mesophases and subsequent highly ordered mesoporous silicate products. The time-resolved in situ X-ray diffraction data of the kanemite−alkytrimethylammonium system indicated that the silica−surfactant mesophase precursor to FSM-16 forms from a medium containing a number of intercalated silicate phases, while in contrast, the hexagonal mesophase precursor to MCM-41 forms from a medium containing no other ordered silicate−surfactant phases detectable by in situ X-ray diffraction.