Influence of silica source on zeolite synthesis in the presence of 1-butanol

Abstract

Synthesis of high-silica zeolites in the presence of 1-butanol (n-BuOH) was conducted under various conditions to explore the role of silica source, aging time, and n-BuOH. It was found that the solubility of the silica source in the aqueous phase was a critical factor for the formation of zeolite precursor when KOH was employed as an alkali source. MPI (ZSM-5) type zeolites were obtained when fumed silica with small BET specific surface area was employed, whereas TON (Theta-1) type zeolites were formed when fumed silica with large BET specific surface area was employed. It was also found that the addition of n-BuOH suppressed the formation of cristobalite. This is probably due to the reduction of the Si concentration in the aqueous phase of the synthesis gel. FT-IR and 13C CP MAS NMR measurements of as-made zeolites suggested that n-BuOH molecules were occluded in the zeolitic pores of TON and MFI type zeolites at the initial stage of crystallization.