Regeneration of Deactivated Hollow Titanium Silicalite Zeolite from Commercial Ammoximation Process by Encapsulating Amorphous TiO2-SiO2 Nanoparticles inside Zeolite Crystal

An efficient regeneration method to encapsulate the poisonous amorphous TiO2-SiO2 nanoparticles within zeolite crystal via post-synthesis has been developed. It is demonstrated that the encapsulation of Ti-rich nanoparticles can reduce the accessibility of H2O2 molecules to acid sites of Ti-rich nanoparticles, thus lowering the inefficient decomposition of H2O2 oxidant during catalytic reactions. Furthermore, the regenerated HTS zeolite is of smaller particle size than conventional TS-1 zeolite due to the existence of deactivated HTS as crystal seed during hydrothermal synthesis. Consequently, the regenerated HTS zeolite shows as high catalytic performance as fresh TS-1 zeolite in phenol hydroxylation reaction with 30 wt% H2O2 aqueous solution as oxidant. Importantly, this study exploits a novel concept on updating the lifetime of industrial zeolite catalyst, which is of both academic and practical significance.