Porous Clay Heterostructures from Al₁₃ Intercalated Montmorillonites: Synthesis and Characterization

Abstract

For the first time, we have used the intercalated montmorillonite with aluminium polyoxocations (Al₁₃) as precursor for the synthesis of porous clay heterostructures (Al-PCHs) materials. They are obtained by simple addition of tetraethylorthosilicate (TEOS) and neutral amines with different lengths (C8 to C12) at a molar ratio of Al₁₃-clay/amine/TEOS close to 1/20/150. The obtained Al-PCHs exhibited higher surface area of 880m²/g and pore volume of 0.85mL/g. The X-ray diffraction, and ²⁹Si MAS NMR indicated the polymerization of silica species in the interlayer gallery, and two different octahedral aluminium conformations detected by ²⁷Al MAS NMR, compared to the starting raw clay. Infrared spectroscopy of adsorbed pyridine suggests the presence of both Brönsted and Lewis acid sites up to 300°C. The thermal desorption of cyclohexylamine was used as further probe to monitor the acidity of the different materials.