Novel layered silicate and microporous silica materials in the Na-magadiite–H2O–(TMA)2O system

Abstract

Novel layered silicate and microporous silica materials have been successfully synthesized in a Na-magadiite–H₂O–(TMA)₂O system. At appropriate water and TMAOH contents, Na-magadiite was converted into a new layered silicate phase (KLS2) at relatively low temperatures, in the range 130 to 150 °C. However, a microporous silica material (FLS) was formed at higher temperatures, from 160 up to 180 °C. The samples were characterized by powder X-ray diffraction, ²⁹Si magic-angle spinning NMR, infra-red spectroscopy, scanning electron microscopy, thermogravimetric and differential thermal analysis, and adsorption measurements. It was found that the KLS2 phase has lower thermal stability than the FLS phase. An amorphous phase was formed upon heating KLS2 below 300 °C, while FLS was found to be stable up to 600 °C and exhibits a surface area of 300 m² g⁻¹ and micropore volume of 0.082 mL (liquid nitrogen) g⁻¹. Factors such as the Na-magadiite, TMAOH and water contents, which dominate the conversion of Na-magadiite, are discussed.