Siloxy defect

Pure silica Beta has been crystallized from alkali-free hydrogel containing tetraethyl-ammonium hydroxide and fumed silica at 413 K by the conventional hydrothermal synthesis method. Characterization has been done by XRD, IR, SEM, solid-state NMR, thermal analysis eind N2 adsorption. The results show that a highly crystalline pure silica Beta is formed. Si MAS NMR reveals that the pure silica Beta has a small number of sites originating from structural defects and almost half of sites are silanol groups. Thermal analysis shows that pure silica Beta possesses nonequivalent sites that are siloxy groups counterbalanced by TEA cations. 

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