Hollow TS-1 crystals formed via a dissolution–recrystallization process

Post-synthesis treatment of a calcined TS-1 zeolite with aqueous solutions of tetrapropylammonium hydroxide leads to hollow TS-1 crystals. By contrast to conventional dissolution experiments using NaOH as mineralizing agent, the creation of intra-particle voids also involves a partial recrystallization of the zeolite. Hollow crystals possess the same chemical composition and approximately the same size as those of the original crystals, but the distribution of Ti species certainly differs. The method reported here is particularly attractive in the case of zeolites contaminated with extraframework Ti oxide species: the formation of the hollow structure is accompanied by a reincorporation of Ti in the zeolite framework, which considerably increases the catalytic activity.