A micro/mesoporous aluminosilicate: key factors affecting framework crystallization during steam-assisted synthesis and its catalytic property

A hierarchical micro/mesoporous aluminosilicate has been synthesized using an optimized steam-assisted crystallization method, by which the material shows perfect crystallization of zeolite frameworks and relatively high surface area and meso/micropore volumes. Key factors for the crystallization of mesoporous frameworks in the process, especially the gel drying temperature, and role of triethanolamine as mesopore template, which have not been addressed before, were identified for the successful synthesis of the hierarchical structure in detail. An energy level schematic was proposed to illustrate the role of the gel drying temperature by affecting the condensation level of the -Si-O-network in the mesoporous framework. Alteration of the experimental conditions within a certain range can yield mesoporous zeolites with varied structure properties, such as surface area, pore volume and pore size. Such hierarchical structures possess remarkably higher catalytic activity in aldol condensation reaction than both amorphous mesoporous materials and conventional ZSM-5 zeolite.