Bulk crystal seeding in the generation of mesopores by organosilane surfactants in zeolite synthesis

Abstract

Zeolites of MOR, CHA, and FAU-X topologies were conventionally synthesized using Na⁺ or an organic structure-directing agent, except that organosilane surfactants were added as a mesopore-generating agent. The organosilanes were represented by the structural formula (CH₃O)₃Si–C₃H₆–N⁺(CH₃)₂C_nH_2n+1, where n was varied from 12 to 16 and 18. Each zeolite synthesis was seeded with a small amount of bulk zeolites of the same structure type. The synthesis result indicated that the bulk zeolite seeds disappeared completely from the zeolite products, indicating their disintegration into tiny fragments that were undetectable by high-resolution transmission electron microscopy. Nevertheless, the zeolite seeding caused a dramatic decrease in synthesis time. More importantly, crystal seeding, in comparison to unseeded synthesis, was highly effective in extending the organosilane-directed mesopore-generating strategy to a wide range of mesoporous and zeolite structures.