Synthesis of nanocrystalline zeolite beta in supercritical fluids, characterization and catalytic activity

Abstract

Nanocrystalline zeolite beta with Si/Al ratios 12.5-50 has been synthesized by applying a two-stage varying temperature synthesis and supercritical fluid aided crystallization. Low temperature nucleation of clear aluminosilicate gel and SCF aided crystallization gave quantitative yields of nanocrystalline zeolite beta in shorter crystallization time without the use of alkali cations and seeded gel. The obtained nanocrystalline zeolite beta catalysts are thoroughly characterized by X-ray diffraction, N₂ adsorption, ²⁹Si and ²⁷Al MAS NMR, IR spectroscopy and Al incorporation in framework was studied by XPS. These nanocrystalline zeolite beta catalysts displayed good activity and high selectivity towards 4-nitro-o-xylene in the nitration of o-xylene when compared to microcrystalline zeolite beta.