Solvent-free synthesis of modified zeolites using hybrid silicas as raw material

The use of hybrid silicas as the silica source in solvent-free zeolite synthesis was investigated as an alternative approach to obtain hybrid aluminosilicates without postsynthetic modification. Hybrid silicas bearing alkyl, amino and mercapto groups were produced by acid catalysis, base catalysis, two-step and silicate sol-gel routes. The influence of the structure and chemical nature of the hybrid silica source on zeolite formation under solvent free conditions was evaluated. Zeolites based on the silicas synthesized by acid catalysis, base catalysis, two-step, and silicate sol-gel routes showed 51, 100, 18 and zero percent crystallinity, respectively. Furthermore, increasing the alkyl chain from a methyl to an octyl or octadecyl loaded onto the hybrid silica increased the time needed to obtain a crystalline structure from 24 h to 48 or 72 h, respectively. For all the systems, a zeolite sodalite was obtained. Thus, the results show the influence of the structural and chemical nature of the silica source on the crystallization process while keeping the sodalite arrangement for all of the conditions.