Green synthesis of hierarchical NaY zeolite for efficient Knoevenagel condensation

Hierarchical aluminum-rich zeolites show promising potential in the Knoevenagel condensation; however, their synthesis is hindered by high cost and energy consumption. To address this, a green synthetic route has been developed for preparing hierarchical NaY zeolite using submolten salt (SMS) activated perlite as the sole source of silicon and aluminum. Systematic characterization reveals that the NaY zeolite synthesized from SMS activated perlite exhibits high purity and crystallinity. This aluminum-rich NaY zeolite, with a framework SiO2/Al2O3 molar ratio of ca. 4.2, possesses intercrystalline mesopores, a large external surface, and abundant basic sites. Investigation of the crystallization process of this hierarchical NaY zeolite indicates that during the initial stage, small crystals assemble and grow on the surface of SMS activated perlite. As crystallization proceeds, the zeolite crystals rapidly grow and aggregate around the activated sample, ultimately forming a zeolite material with a crystal-packed morphology. In the Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate, the synthesized hierarchical NaY zeolite demonstrates higher benzaldehyde conversion compared to conventional counterparts.