RAPID SYNTHESIS OF MFI TITANOSILICATES USING IN-SITU SEEDING METHOD

A new synthesis method for a rapid crystallization of metallosilicates called the in situ seeding method was applied to the MFI titanosilica te (TS-I) synthesis. This method, which involves the preheating of the silicate gel and the consequent generation in situ of MFI silicate (s ilicalite-l) seeds before the addition of Ti source, dramatically acce lerated the crystallization of TS-I in methylamine medium. Ti ions wer e readily incorporated into the zeolite framework as confirmed by IR a nd the unit cell expansion measured by XRD. In comparison, the classic al seeding method achieved under identical conditions yielded Ti-free silicalite-l crystals. The optimal crystallinity of the preheated sili cate gel for the in situ seeding method was evaluated to ca. 5%; a low er amount of silicalite-l seeds led to a slower crystallization of TS- 1, while crystallinity over 5% resulted in the continuation of the see d growth, leading eventually to crystalline silicalite-l. (C) 1997 Els evier Science B.V.