Synthesis of mesoporous Beta and Sn-Beta zeolites and their catalytic performances
Mesoporous Beta zeolite has been successfully prepared through hydrothermal synthesis in the presence of cationic ammonium-modified chitosan as the meso-template. Through a subsequent solid–gas reaction between highly dealuminated mesoporous Beta zeolite and SnCl4 steam at an elevated temperature, mesoporous Sn-Beta has been facilely obtained. It was revealed that the addition of cationic chitosan induced the nanocrystal aggregation to particle sizes of ∼300 nm, giving rise to the intercrystalline/interparticle mesoporosity. In the Sn-implanting procedure, Sn species were demonstrated to be doped into the framework of the resulting mesoporous Beta zeolite in a tetrahedral environment without structural collapse. Due to the micro/mesoporous structures, both mesoporous Beta and Sn-Beta exhibited superior performances in α-pinene isomerization, Baeyer–Villiger oxidation of 2-adamantanone by hydrogen peroxide and the isomerization of glucose in water, respectively.