The synthesis of hierarchical high-silica beta zeolites in NaF media

An aerosol-assisted hydrothermal method has been applied to synthesizing hierarchical beta zeolites with SiO₂/Al₂O₃ ratios ranging from 44 to 392 in NaF media. Two different morphologies, including nano-aggregates with interparticle mesopores and plate-like zeolites with intracrystalline mesopores, can be formed depending on the SiO₂/Al₂O₃ ratios of the synthesis gels. A possible mechanism for the formation of the beta zeolites has been proposed. The obtained beta zeolites show hierarchical pores, good Al species distribution and less internal defect sites. Evaluation, by the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPB), is consistent with the acidic properties and the pore structure of beta zeolites with different ratios of SiO₂/Al₂O₃.