Rapid synthesis of MFI titanosilicates using in situ seeding method

Abstract

A new synthesis method for a rapid crystallization of metallosilicates called the in situ seeding method was applied to the MFI titanosilicate (TS-1) synthesis. This method, which involves the preheating of the silicate gel and the consequent generation in situ of MFI silicate (silicalite-1) seeds before the addition of Ti source, dramatically accelerated the crystallization of TS-1 in methylamine medium. Ti ions were readily incorporated into 1he zeolite framework as confirmed by IR and the unit cell expansion measured by XRD. In comparison, the classical seeding method achieved under identical conditions yielded Ti-free silicalite-1 crystals. The optimal crystallimty of the preheated silicate gel for the in situ seeding method was evaluated to ca. 5%; a lower amount of silicalite-1 seeds led to a slower crystallization of TS-1, while crystallinity over 5% resulted in the continuation of the seed growth, leading eventually to crystalline silicalite-1.