Al-Rich Zeolite Beta by Seeding in the Absence of Organic Template

摘要

Low- and no-template precursor suspensions are studied to clarify the effects of Si/Al ratio, seed content, heating temperature, and crystallization time on the syntheses of Al-rich zeolite Beta. Syntheses using 2.5 wt % seeds resulted in well-shaped octahedral Al-rich Beta crystals with sizes between 0.4 and 1 μm after either 6 days hydrothermal treatment at 125 °C or 12 days at 100 °C. The crystalline Beta product has Si/Al ratios as low as 3.9 (16.4 Al atoms per unit cell), which are comparable to the natural counterpart of zeolite Beta, the mineral Tschernichite, and give the material high hydrophilic properties. The tetrahedral coordination of aluminum in the Al-rich Beta and their stability upon calcinations is demonstrated by NMR spectroscopy and TG analysis. The seed method opens new perspective in the development of economically and environmentally friendly synthesis approach for Al-rich zeolite Beta, where the amount of organic template is reduced significantly.